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Hi,
I am trying to create some kind of a viewer that can view files in different formats like:
Text(ASCII), Text(UNICODE),Bin, Hex, Oct.
the last two require dealing with bits, (3bits --> 1 oct), (4bits-->1 hex), so what is the fastest way to do this? I need to boost performance
Thanks
Mohammad
Well, I am not sure about octal, but there is nothing easier or more "user friendly" than hex.
For example:
Code:
CString msg;
BYTE arrayOfByte[3];
msg.Format(_T("0x%02x 0x%02x 0x%02x"), arrayOfByte[0], arrayOfByte[1], arrayOfByte[2]);
MessageBox(msg, _T("Hex string"));
There are several operators in C++ language to deal with bits. For one thing you can use masks and binary operators to determine values of individual bits.
Any programming book will have a whole chapter dedicated to bit operations.
Yes friend,
I know the basics of bitwise operators, I have been programming C++ for more than 5 years, but I just wonder if there is someway that is significantly faster than the usual way
Thanks
Mohammad
Hi all,
I'm new to Android development, kind of a Java noob, but not to programming in general. I'm not looking for code examples, just theory or a basic 'how this is done' in Java/Android. I also hope this will become useful information for other developers heading down this path.
I've had some success creating my first Android app - I apologize for not going into details about the specifics of the app, as I plan to eventually sell it commercially on the market - the question should, however, be applicable to any application using this flow model.
My current goal for this application is to create a 'plugin' type system ( like those used in OpenHome and other apps that allow user-generated plugin-able content / functionality ), to allow for flexibility in both my own further component development, as well as eventually creating an open interface for other developers to use to extend the application.
Currently my application is laid out as follows:
Main UI class
- entry point to the application
- starts the service class to spawn 'spinners' ( data processors )
- presents the user with an (ideally) extendable interface to the service
- binds to the service class using AIDL
Service class
- presents an AIDL interface for communication from the UI process
- creates 'spinners' of various types based on user interaction that process data
- persistent, will run in background, new Main UI instances will connect to the running service and present the currently running spinners.
- extendable via an as-yet-unimplemented plugin interface to add new types of spinners
Spinner classes
- use a generic interface with a handfull of common methods to communicate with the Service class, bubbling up data to the UI interface.
- processes user defined data streams, outputs to a buffer/sink suppled by the Service
Assumptions I can make are:
- the plugin (Spinner) class will always implement / override a group of methods to present to the Service class; ie 'putData()', 'getStatus()', 'start()' and 'exit()'
- the plugin class should always return data to the Service class via a supplied/shared buffer ( short array, for example )
Where I'm stuck at the moment is exactly how to implement extendable classes without those classes being a part of the current code base package. More simply, how do I interface with these classes without knowing their names, methods, etc?
As mentioned, I'm new to Java so I may just be overlooking an already implemented class that handles this interaction. If that is the case, I'd be happy for anyone to tell me to shut up and read the docs, if you can point me at the proper docs
What I really don't want to do is create a 'plugin language' for these external bits, as I feel this could hamper development of fast/functional plugins vs. those written as native Java classes. This would also expose potential security issues, as I'd need to create a public interface to the Service class for these applications to link to. I'd prefer if execution of the plugins remained private / internal to the 'main' application.
I'm already using an AIDL interface between the UI class and the Service class - it would potentially be possible to use further AIDL interfaces into each plugin, but from my romp-through-the-park implementing the UI -> Server communication in this way, I find it cumbersome and difficult to pass any kind of complex data sets/controls. And I'm still unsure how the Service class would actually implement these without inheriting the interface directly.
I've poked around Intents in Android, but I'm having trouble wrapping my head around them/what they're for - it seems it might be possible to inherit the plugins that define themselves as sinks for my applications specific Intent type, but I'm lost in the details of how this works exactly, or if it would even be a viable path for what I'm trying to do. Can new Intents even be introduced into Android?
I apologize for the long-winded explanation of what boils down to a simple question:
How can I implement a 'plugin' interface in my application to allow myself and other developers to extend my app through their own classes?
I've been a Java developer for 10 years or so.
From what I understand the "Android" way, would be intents. I'm still working on wrapping my brain around them too.
However, the "Java" way would be to define an interface (or several) for the plug-in(s) to implement. Then use reflection to identify classes in the classpath that implement that interface.
There are some advanced techniques using custom class-loaders, but researching reflection should get you started; if you choose to go that route.
Thanks for the quick response, I'll take a look at the reflection implementation.
Intents do seem to be the 'way to go' for inter-application communication in Android the more I read about it though - if I can figure out how to pull in plugins which specify my applications 'Intent' dynamically. Intents seem to work really well for spawning a 'dumb instance' of an application - like the browser when clicking a link in another app - when your application doesn't want to deal with that data locally.
Seems a bit more difficult to wrap them around a bi-directional interface between the service and the external plugin application. If anyone's got experience with this kind of thing I'd definitely appreciate prodding in the right direction. Documentation on Intents is confusing at best.
Hello XDA, I'm trying to write (what I believe to be) a simple app; a calculator with storage buttons. I've gotten the basic layout and initialized the core components. Yet, when I add on-click listeners, there's a force quit when testing. Attached is the Java class and xml. I've tried very hard to figure out what it is; I've even tried simply putting a println statement in the on-click listener. It doesn't even do THAT
Also, if there's anything (AT ALL) that you could criticize me on in terms of code organization, standards, etc. PLEASE let me know. I'm a newbie, and it's better to kick bad coding habits before they grow strong!
Thanks in advance, guys. I know it's annoying to debug others code, especially beginners, but I don't think it'll take much time at all, and I'd like to think I'm a relatively organized beginner
So I found out what it was; EditText doesn't accept ints or doubles as parameters. There's got to be an easier way of doing this, though. Is there any calculator-window-type objects that will store ints and/or (preferrably or) doubles? It's doable, but highly annoying to cast everything to a string and then parse it back to a numerical data type to perform operations on it.
During recent development of my app (see my signature) I focused a lot on how to optimize the already working code further in order to make it smoother without loosing quality or using too much memory. Well I came across some mistakes I had made in my early days of developing Android so I figured it might help the beginners and intermediate developers. So here I collected my suggestion of common mistakes and best practices in Android. Let me start by making you familiar with a motto which you might know if you have developed Perl before.
TIMTOWTDI
There's more than one way to do it, in short TIMTOWTDI is a well known aspect of the Perl language, which aims at giving programmers the freedom to choose their way of doing things. It “doesn't try to tell the programmer how to program.” Well it does have various disadvantages such as possibly messy code and barely readable code, but it offers programmers to use their preferred style.
The only reason why I'm bringing this up here is because it helped me a lot to think that way, since TIMTOWTDI sometimes applies to Java as well and a way somebody else is preferring might not be better than your own way. But it is never bad to have a look at how others code the important tasks and sometimes the performance or readability gain is tremendous. So I'm not telling you to exactly use my way, but advice all beginners to perhaps rethink their code .
Tweaking Android Apps
The first step is always to look at what the awesome Android documentation says about performance, so I can more than advise you to read this straightforward article about what to do and not to do on Android. It covers some very important performance issues like the expensive object creation and method invocations. It is crucial to follow those basic rules while trying to develop fast Android apps. I will cover and further explain some of their suggestions here, but will try to also look at them from a developer's perspective who cares about readability and simplicity.
Now onto the code, let's start with some basic Java practices and then move on to some more Android specific styles and improvements.
Looping wisely
Often it doesn't matter if you write slow code and lose 1 or 2 milliseconds but especially in loops and everything that can be called once a frame you suddenly loose a lot of time. Thus it is crucial to especially pay attention to those repeated parts of your code like the onDraw() method in your custom view implementation (see last section) and start optimizing there. Let's take a look at what kinds of loops we have, the slowest first and the fastest ones towards the end:
while
The while loop is probably the first complex programming structure you learned, and just writing
Java:
success = false;
while (!success) {
trySomething();
}
is extremly readable but can potentially run forever or longer than you need it to. One aspect which is often overlooked is that the condition inside the parentheses will be checked on every run of the loop! So even a simple string.length() call can be optimized (if the String won't change) saving its length as an int and then using that in the condition block.
Its unpredictability and lack of possible tweaking done by the JIT makes the while loop a tool that needs caution but is sometimes crucial to complete the task. Just make sure you only use the while loop if there is no way to predict when your condition is false. For almost all other cases, you can do some calculations and use one of the iteration loops:
for (traditional)
This one is widely used like this:
Java:
for (int i=0; i<getSize(); i++) {
doSomethingWithIndex(i);
}
Even though this is more predictable, consider how the program will run: Before every execution of the block, the condition i<getSize() has to be checked, so getSize() is called (and an Android, method calls are expensive!). You could now think, alright, we'll just cache our size upfront like we did with in our while loop, but examine the following fast example of iterating through an array:
Java:
for (int i=getSize()-1; i>=0; i--) {
array[i] = getNewValue(i);
}
The trick is starting at the last value and then iterating backwards until 0 is reached. This may not work at all times, where the order of the blocks may be important or it is redundant due to having a fixed end value, but it saves both method calls and memory usage needed to get the last value before going into the loop.
But that is hardly readable and you often have to rethink because of looping backwards, so we can do better can't we?
for (iterator-based: “foreach”)
Dealing with an array, List or other collection of data you can easily do something for every part in that collection using the foreach loop:
Java:
for (Object item : objects) {
doSomething(item);
}
That is the fastest way you can iterate through any kind of iterable collection because it can be heavily optimized by the compiler and is also simplistic and readable. The only problem here is that you don't have the index of the item you're getting and you can't write data to the collection. To accomplish that one of the slower for loops must be used.
Keywords do matter
This is a minor one that is overlooked often. Beginners in Java mostly don't use keywords and access modifiers like “private”, “public”, or “final”. That is fine since we all love simplistic code don't we? And an honest word, if you don't write a library or work on your code with a big team, you don't have to know much about the access modifiers, but if you want to, there is always the Java documentation. But the “final” identifier is actually pretty important to both the ones reading the code and also the compiler, since it can just insert its value into the references. That means, that whenever you declare an instance variable, think about if it is likely to change or if you can declare it as final. Within methods, making use of the “final” keyword does not really change much for the compiler, but it sometimes helps you make a clearer design so you directly get a compiler warning whenever you're trying to change a final variable's value.
A side note on making “static” variables and fields – I wouldn't recommend that on Android unless you know what you're doing or you're using it together with “final”. A “static final” instance variable is the best way to declare constants in Android because the compiler can replace it fast and ART can replace it during the install of your app!
Strings are special
Let's talk about something that is fundamental to Java – the String object. Well it's not a real object since it is actually immutable. That means a String can only be created or collected by the garbage collector, it can't be changed (which is very important since object creation is god damn expensive in Android so it would make our apps pretty slow)! Wait, then what happens if I call one of the awesome methods in the String class like substring() or replace()? And here comes the downside: These methods have to create new Strings and the old one is collected by the garbage collector. While this might be totally alright if you're just parsing some basic user input, if you need to perform some heavy String operations like many substrings, a whole lot of unused garbage and overhead is created. This doesn't only mean that you are temporarily using a lot of memory, with the garbage collector needed to kick in it also affects your performance.
So how do we get around this problem? Luckily there is a Java class which can do almost the same as the default String implementation, the StringBuilder. This class will hold a char array with all the chars you had in your String. The class can take care of managing that array like initializing it with a default length of 16 and creating a larger array once you have more characters that would fit into it. Take a look at the constructors as well – with new StringBuilder(length) you can directly make that array as long as it needs to be and with new StringBuilder(string) the array is instantly filled with the string. The big advantage the StringBuilder is that it can modify the array instead of having to create new Strings every time. If you're finished with the heavy modifying, just call toString() to get the String back.
If you want to read more about it, here's a nice article.
Android-specific tips
Bundling is better than trundling
Let me explain this with an example: Let's say you are dealing with some data concerning persons so you are saving their name, age and gender. In any object oriented language like Java you would create a wrapper object holding that data:
Java:
public class Person {
private String name;
private int age;
private boolean isMale;
public Person (String name, int age, boolean isMale) {
this.name = name;
this.age = age;
this.isMale = isMale;
}
// additional getters and setters go here.
}
Of course you could do that in Android as well, but you will encounter this problem: What if you need to save your Person array or need to pass a specific Person to another activity? Well, you have a few options available:
You could override the toString() method in Person so it contains all its data and parse your array into a String array manually. Then another constructor will be needed to get the data back from the String using our beloved String operations. But there is still the problem that when you want to add data to the person like height later, you have to reconsider the toString() method and it's constructor counterpart.
Alternatively, wanting to integrate it better into the system, you might want to implement Parcelable in the Person class. That way you can directly put person extras to your Intent or save it to SharedPreferences. But that seems like more work if you want only a simple container for your data. Once you need have a more complex class it might be advisable to make it Parcelable (perhaps using the Android Studio plugin, thanks @nikwen), but let's start with an easier apporach here.
This is how I do it: I use a Bundle instead of a person class to store all the needed data. The Bundle class already implements Parcelable and and simplifies adding data for you. What is more, you are probably already familiar with it since you get one calling getExtras() on the starting Intent of your activity! Now back to the example, this is how it would be done:
To not get confused about all the keys you need, let's create a class containing some static final keys:
Java:
public class Person {
public static final String NAME = “person_name”; // will contain a String
public static final String AGE = “person_age”; // will contain an int
public static final String ISMALE = “person_ismale”; // will contain a boolean
}
While this is only needed for consistent keys, here is how you would create the Person:
Java:
public Bundle getPerson(String name, int age, boolean isMale) {
Bundle person = new Bundle();
person.putString(Person.NAME, name);
person.putInt(Person.AGE, age);
person.putBoolean(Person.ISMALE, isMale);
return person;
}
Similarly, you can get one or more stored values of the Bundle using one of the person.get...() methods. Furthermore, instead of creating an array of Persons you can now create a Bundle of persons using bundle.putBundle()! You just need to find the right key-scheme, here you could either provide an id for each person or just use their names as key (although the key array has to be passed seperately). And what do we get from all this? Well we can now just call intent.putBundleExtra(person) and voilà, we've passed it to another app component.
Resourcing is not outsourcing
One of Android's big advantages is its exceptional resource system. The fact that all your Strings and values are saved in a separate xml file makes your app not only easier to translate, but also keeps your code cleaner and lets you have a complete overview of what amount of constants you use. But you can go further than that. The resources allow for entirely different configurations depending on screen size, resolution, orientation, location and api-level! To learn more about how this can be done, head over to the Android devoper guides.
One thing I wanted to highlight is that it used to be quite hard to make a consistent interface and still support Android 2.1 and above. That is not the case any more since we now the the continuously improving AppCompat library. It is even useful for apps targeting only ICS and above because it contains bugfixes and improvements for those versions as well. Using this library is the best way to get the holo theme and its ActionBar in your app, although if you could also try ActionBarSherlock to accomplish the latter.
Click to expand...
Click to collapse
Think D.I.P
So what's this strange thing they call dip? And why do we even bother using it, we have had pixels (pix) since the beginning of programming. First things first, try to avoid pixels on Android. On almost every other platform using the smallest unit that's available is a great thing in layouts, but not so much on Android where apps can run on devices as small as a smartwatch up to 2k tablets. The problem is that you can't be sure if a single pixel is as small it can barely be seen or as large as a few millimeters. That is why we have the standard-sized density-independent-pixels (dip or dp in short) where 48 dips are roughly equivalent to 9mm, the convenient size of a touchable area (e.g. a Button). Great, then how many dips is my screen wide/high? That is not an easy question since it varies as well. Phones usually have around 320dips (at the smallest width) but larger screens can fit more so on tablets you have 600dips or more. Try to understand this documentation and don't be confused with the abbreviations dp, dip and DPI – dp and dip are the same and DPI is dots per inch (similar to pixels per inch), the screen density!
The reason why I'm bringing this up here is advice you to understand and always think in dips, never in pixels. Even on a Canvas, where there is only methods for pixels, don't think “ok I draw my text 20 pixels from the left edge and 50 from the top so canvas.drawText(“text”, 20, 50, myPaint);”. Start to think in dips: “I have to draw it 16dip from the left edge and 24dip from the top!” But how to convert it to pixels so it can be actually drawn onto the Canvas? It really is a shame there is no method in the Context class to directly convert dip to pixels, so here's the one I use:
Java:
private DisplayMetrics displayMetrics;
/**
* Converts a given dip (density independent pixel) value to its corresponding pixel value.
* @param dips The dip value to convert, as float.
* @return The pixel value, as int.
*/
private int dipToPix(float dips) {
if(displayMetrics == null)
displayMetrics = getResources().getDisplayMetrics();
return (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, dips, displayMetrics);
}
And a side note on sp, that is the scale-independent text size. Try to use it as far as you can, for instance in layout resources. But just in case of needing the actual size, use the same method because sp is computed almost the same as dip.
Hyperthreading is not that complex
An app's UI (or “main”) thread is its beating heart, and we don't want to slow down what's powering us if there are other options available, right? If you don't follow the rule of not performing any time consuming tasks in the default thread you'll end up with what all developers fear: The “App is Not Responding” dialog – in short ANR. When users see this, they can get really mad, from just force closing your app and uninstalls to 1-star ratings everything is to be expected. Because it is crucial to know about Threads (and Processes), carefully read the guide in the Android docs about it, pay special attention to the two simple rules in Android threading:
1. Do not block the UI thread
2. Do not access the Android UI toolkit from outside the UI thread
Click to expand...
Click to collapse
Let's take a look at the first one, what are you going to do instead if you need to accomplish an expensive task like web requests, complex calculations, Bitmap operations, database queries and I/O management?
Well the answer is not as simple as it may seem since it depends on what and how often you will be doing that task. A task that is performed once per activity launch is almost always wrapped into an AsyncTask, a class which is heavily optimized and integrated into the system. If you know how it works it is a very powerful tool since it does most of the heavy lifting for you, so let me show you how to do it:
You start by extending the AsyncTask class like so:
Java:
private class MyAsyncTask extends AsyncTask<Param, Progress, Result> { //...
Usual stuff, except for the weird <Param, Progress, Result> thing. It is actually not that hard, these are all just type declarations of variables your methods want to use. Thus, the first one is the type of starting parameter you want. Think of it as if you wrote your task in a separate method without access to any instance variables, what data would it need to work (what params would you pass to it in the parentheses). The second one is actually often unused and is needed if you want to return a var indicating progress on the task so it can be published e.g. in a ProgressBar. Lastly, Result is (you may have guessed it) the type of variable you want your task to return, to be published in the UI as well. A typical configuration would be <Uri, Integer, String> for a task reading a file. Note that these have to be objects, so for primitives you'd have to use their respective Java classes like Integer or Double. But that also means that a Bundle can be used as well so we know how to pass multiple parameters now! And there is another way as well, look at the overridden methods:
Java:
protected Long doInBackground(Uri... uris) {
// do your expensive work here, it runs on a separate thread!
}
protected void onProgressUpdate(Integer... progress) {
}
You'll notice the three dots after Uri and Integer. To keep it simple, treat it as an array, so to access your value call uris[0] and progress[0], respectively. The reason for it being an array is that you can start the same AsyncTask with multiple parameters of the same task:
Java:
new MyAsyncTask().execute(uri1, uri2, uri3, uri4);
This is extremely useful in this case to read multiple files at the same time (don't be confused with the configuration in <> above, the param(s) passed to execute() are joined together in the Param array).
A side note on progress here, if you want to publish progress during your doInBackground(), just call publishProgress(Progress) and override onProgressUpdate() to publish the changes in the UI. Similarly with onPostExecute(), you'll probably want to override that method as well to show your awesome result to the user.
What you need to keep in mind is how AsyncTask is handled internally, read the section “The 4 steps” in the AsyncTask documentation carefully. In fact, doInBackground() is method you need to think about the most since it is encapsulated in a separate thread with no access to the UI or methods in your activity.
Because AsyncTask is limited to one operation and should only run up to a few seconds, there are a couple of other ways to do tasks in the background like a second Thread and helpers such as Handlers. The Handlers are needed to access the UI from the worker threads, still following the second rule above. If you want to read more here's an awesome Vogella tutorial about it.
Fragment-tation
This next one is really a good style of development and can save a lot of work if you provide layouts for both phones and tablets (which you definitely should). The basic theme of using Fragments is to follow the divide and conquer technique, which dates back to ancient time in Babylonia. Thus, the idea is to have one large problem (a user interface and its data for both tablets and smartphones) and split it into multiple simpler ones (in this case having one or more Fragments for each screen on phones). Especially in multi-pane layouts, for instance in the settings app, Fragments are a wonderful tool to avoid the use of two different activities, one for phones and one for tablets. The steps to implement them in your app are pretty simple and there are already some neat guides like the one in the documentation and Vogella's one. An additional use-case for Fragments is to retain an AsyncTask when rotating the screen. You would create a Fragment without layout in the UI and call setRetainInstance() on it. Any expensive AsyncTask can then be started inside that Fragment and is not stopped when the activity is recreated during an orientation change.
Memory-zing is unneeded
But it is not only performance, layout and style which can be improved, think about memory usage for a second. It goes hand in hand with performance since an app which consumes unnecessary memory (garbage) will be slowed down by the garbage collector (GC) thrown in from the system, trying heavily to free some RAM. On Android this is extremely important, since a garbage collector running intensely on a single or dual core processor can really slow down the device's performance. That is also why method calls and object creation are so expensive and have to be used with caution – the overhead they produce bumps up the memory usage. And there is one specific case where you can really have a problem with your memory, a so-called memory leak. What this means is that some part of your app is holding on to a very large object like a Resources or database one or even a whole Activity or Fragment. The problem is that the GC can only collect objects which aren't referenced from an active part of your app so this means it can't be collected and ends up blocking all your available memory. Such a leak is something you want to avoid at all times and there are some awesome tools to find out if you have one. All you need to know about that and memory optimizations in general is covered in this amazing I/O talk, so I advice you to watch that!
Most of the time there is no real need for reducing method calls and object creation because the GC is fast enough. But there is one step where it is crucial to avoid it, methods which are called on every redraw like the onDraw() method of a View, which I'll cover in the following.
Optimizing performance? onDraw!
In your custom views the most important method to think about is the onDraw() method since that is where everything that is visible to the user is rendered. A lot can be gained (or lost) in that crucial step, so try to follow the performance guidelines posted earlier as close as possible. Especially, pay attention to the object creation, creating a few objects in onDraw() might not seem expensive, but the memory footprint and the garbage collector usage will be tremendous. When drawing on a Canvas for instance, a common pattern would be to check if the paint instance variable is null before drawing:
Java:
if(paint == null) {
paint = new Paint();
paint.setColor(drawingColor); // ...
}
That code would typically be placed in the surfaceCreated(), but could also be in the onDraw() if you are lazy and want to keep it in one place. . While object creation is not the only thing you can improve performance-wise, just try to apply the aspects I wrote about in the beginning, especially those loops!
One thing I have to point out about performance before moving on to some links that might help you is that before trying to optimize your app in some arbitrary way (and totally destroying readability) measure upfront. That means use the tools mentioned in this great I/O talk covering graphics and performance to get a sense whether your app is really driving close to that 16 millisecond threshold to get the desired 60 frames. Additionally, it might be a good idea to not only test it on the high end devices (#Nexus5) but also those with a high “resolution/processing” value such as the first tablets with 1080p resolution. Thus, only start tweaking performance if you know you take too much time, then try to nail down the time consuming methods. And always try to improve readability and simplicity, not only for us when posting pieces of your code here but also for yourself: it helps getting into the flow if you see that your code is readable and nice .
Additional resources
If you can spare some time and want to know more about how to build awesome apps and UIs, check out the Android sessions at Google I/O 13, especially the Android UI design talk and the Android Protips 3 (but the first and second Protips were great as well as the beginner's talk from 2010). There is also the Android developers blog and the Vogella tutorials. As usual, the Android developers page is always a great resource and Google is still your friend (use “android dev” together with your question to get better results). For more info about general Java performance improvements, I found this nice pdf outlining how you can improve your code even further.
Click to expand...
Click to collapse
</guide>
Anyway, that's about it. It has really become a way too long collection of links and videos so I hope it was useful and perhaps made you rethink your code . If you've got any comments or suggestions feel free to post them here, helps a lot.
This guide was featured on the portal on February 4th (thanks eagleeyetom!)
To be continued...
One Thanks isn't enough!
Great writeup! Thanks!
Wow man such a good information muchly appreciated great job!
Sent from my Nexus 4 using Tapatalk
Wow, great collection of tips and tricks. Much appreciated!!
Handy tips
awesome job dude.was really helpful!!!!!:good:
Great article! Please keep going. :good:
Simply awesome...great work.
Sent from my SAMSUNG-SGH-T989 using Tapatalk
Thanks for this great writeup! The android specific tips are really interesting.
Great guide (again). :good:
Just one thing I want to add: I still prefer wrapper classes which implement Parcelable. In fact, it's not that difficult and you should be able to do it in a few minutes. Have a look at the example code here: http://developer.android.com/reference/android/os/Parcelable.html That's it.
I've also found an IntelliJ plugin for that purpose (but I haven't tried it yet): https://github.com/mcharmas/android-parcelable-intellij-plugin
That wasn't meant to degrade your work though. It's an amazing guide.
nikwen said:
Great guide (again). :good:
Just one thing I want to add: I still prefer wrapper classes which implement Parcelable. In fact, it's not that difficult and you should be able to do it in a few minutes. Have a look at the example code here: http://developer.android.com/reference/android/os/Parcelable.html That's it.
I've also found an IntelliJ plugin for that purpose (but I haven't tried it yet): https://github.com/mcharmas/android-parcelable-intellij-plugin
That wasn't meant to degrade your work though. It's an amazing guide.
Click to expand...
Click to collapse
Good point and thanks!
Having a closer look at it, implementing Parcelable is not that much work and it would definetely be the more advanced way. Bundle is basically just another layer that makes things a bit easier for the start (and no typecasting) and I found that it can really shine with a singleton class holding the keys and the getters and setters (which have an additional param, the Bundle). For a beginner who just wants to save some values (possibly keeping the keys in the activity or even hardcoded) using the Bundle is a lot easier. Yet again, TIMTOWTDI
Thank you!
Hey Simplicity, after few years there is something you would change? Maybe dagger2, kotlin, rxjava changed the game, as really open question what do you think about?
The question might be a bit off topic, i am working on a root app development but i am pretty confused that how should i get the busbox commands to run on button press, i have given the path and everything but how am i supposed to create a busbox file in data/data/package/files.
This part is confusing me I am not able to create that file, should i keep it in res while creating the app ? And also one last question, from where can i get that busbox file with all its command. Please help, I'm sorry if this is the wrong forum I'm new to posting questions and also to app development .
Hello,
I create that thread to share with you a tutorial showing you how to access the Java 8 language features with Android N. You can find the tutorial here on my blog : http://www.ssaurel.com/blog/accessing-to-the-java-8-language-features-with-android-n/ . There are also others great tutorials for Android development.
If you prefer to read the tutorial here, this is the complete content :
Accessing to the Java 8 language features with Android N
Google has unveiled developer preview of Android N last month with a new exciting developer program. Official release is planned for Q3 2016. Amongst the new features of Android N, the support of several Java 8 language features is a great addition for developers.
Supported features include :
Lambda expressions
Default and static interface methods
Repeatable annotations
Method References
Additionally, some new APIs introduced with Java 8 are available like reflection and language-related APIs and Utility APIs (java.util.function and java.util.stream).
Set up your development environment
To support Android N new features, you need to set up correctly your development environment. You need to get last version of Android N developer preview and to download Android Studio 2.1. You can make these installations via the Android SDK Manager on your computer. To get more details about the installation process, don’t hesitate to read the official documentation from Android Team : http://developer.android.com/preview/setup-sdk.html
Enable support for Java 8
In order to use the new Java 8 language features, you need to use the new Jack toolchain. Jack, for Java Android Compiler Kit, replaces javac compiler. It compiles Java language source code into Android-readable dex bytecode with its own .jack library format. Furthermore, it provides other great toolchain features inside a single tool like repackaging, shrinking, obfuscation and multidex. Before Jack, you needed to use ProGuard to achieve these tasks for example.
To enable support for Java 8 in your Android project, you need to configure your build.gradle file like that :
Code:
android {
...
defaultConfig {
...
jackOptions {
enabled true
}
}
compileOptions {
sourceCompatibility JavaVersion.VERSION_1_8
targetCompatibility JavaVersion.VERSION_1_8
}
}
Enjoy your first Lambda Expression on Android
Now, you can enjoy your first Lambda expression on Android. Basically, a Lambda expression is a block of code that can be passed around to be executed later. In fact, it is very similar to anonymous classes. However, Lambda expressions are succinct with less verbose code. Let’s use a Lambda to set a click listener on a Button :
Code:
button.setOnClickListener(view -> Log.d(TAG, "Button Clicked."));
You can make the same with an item click listener on a ListView :
Code:
listView.setOnItemClickListener((parent, view, position, id) -> {
// …
}
It works great with a Runnable interface too :
Code:
Runnable runnable = () -> Log.d(TAG, "Log from a Runnable with a Lambda");
newThread(runnable).start();
Clearly, you can see the code is shorter and more readable with Lambdas expressions. It will be great for the productivity of Android developers.
Create your first Functional Interface on Android
To create our first Functional on Android, let’s take classic example of a Calculator with an addition feature :
Code:
@FunctionalInterface
public interface Calculator {
int calculate(int a, int b);
}
Now, you can add a default method to the Calculator interface that will be used to display a result for example :
Code:
@FunctionalInterface
public interface Calculator {
int calculate(int a, int b);
default void print(String result){
// … print result …
}
}
Finally, we can create a Lambda expression with that interface :
Code:
Calculator c = (a, b) -> a + b;
Like you can see with those simple examples, Java 8 language features will offer a new way to Android developers to improve their productivity. Thanks to the developer preview of Android N, you can try these features right now.
Don't hesitate to share your feedbacks with me.
Thanks.
Sylvain
Is it worth going to Jack right now, though?
I've read that it's slower in build time than the normal configuration, and as some apps already take a huge amount of time to compile, I'm not sure if it's worth it.
Also, lambdas are only syntactic sugar, right? Behind the scenes, everything is still the same.
AndroidDeveloperLB said:
Is it worth going to Jack right now, though?
I've read that it's slower in build time than the normal configuration, and as some apps already take a huge amount of time to compile, I'm not sure if it's worth it.
Also, lambdas are only syntactic sugar, right? Behind the scenes, everything is still the same.
Click to expand...
Click to collapse
For the moment, I just tried on small projects. So, it was not so slow during build time. May be on big projects ?
These new features are not a revolution for sure, but it's interesting to have the choice to use it in the future when you develop Android apps. Be able to have some functional programming features is a good thing.
For Lambdas, it's not really the same thing on the bytecode. On Java 8 desktop apps, some benchmarks showed that using Lambdas is very often faster.
sylsau said:
For the moment, I just tried on small projects. So, it was not so slow during build time. May be on big projects ?
These new features are not a revolution for sure, but it's interesting to have the choice to use it in the future when you develop Android apps. Be able to have some functional programming features is a good thing.
For Lambdas, it's not really the same thing on the bytecode. On Java 8 desktop apps, some benchmarks showed that using Lambdas is very often faster.
Click to expand...
Click to collapse
I see.
For Lambdas, I don't know. It's just my guess that whatever you write is converted to normal code that you probably should have written without lambdas.
Perhaps the JDK has some optimizations for it.
EDIT: it seems there is a difference:
http://www.oracle.com/technetwork/java/jvmls2013kuksen-2014088.pdf
http://blog.takipi.com/benchmark-how-java-8-lambdas-and-streams-can-make-your-code-5-times-slower/
Nice. Wonder if it's this way on Android too.
AndroidDeveloperLB said:
I see.
For Lambdas, I don't know. It's just my guess that whatever you write is converted to normal code that you probably should have written without lambdas.
Perhaps the JDK has some optimizations for it.
EDIT: it seems there is a difference:
http://www.oracle.com/technetwork/java/jvmls2013kuksen-2014088.pdf
http://blog.takipi.com/benchmark-how-java-8-lambdas-and-streams-can-make-your-code-5-times-slower/
Nice. Wonder if it's this way on Android too.
Click to expand...
Click to collapse
Thanks for the links. Really interesting.
It seems you were right. Lambdas and Stream can make execution slower.
sylsau said:
Thanks for the links. Really interesting.
It seems you were right. Lambdas and Stream can make execution slower.
Click to expand...
Click to collapse
They do? I thought the data and graphs show Lambdas are faster. Are you sure?
AndroidDeveloperLB said:
They do? I thought the data and graphs show Lambdas are faster. Are you sure?
Click to expand...
Click to collapse
It depends the way you use it like said on takipi blog. If they are well used, it can make your code run faster however. It's always the same thing, it depends from your implementation and the way you use it.
sylsau said:
It depends the way you use it like said on takipi blog. If they are well used, it can make your code run faster however. It's always the same thing, it depends from your implementation and the way you use it.
Click to expand...
Click to collapse
So there is no definite conclusion? So my guess is that for Android it's too early to see difference between normal code and Lambda.
Pretty Information
such a nice post, i am studying the java but it is totally different why can you please explain what the java in book is different the java in applications??
Regards Junaid Shahid
---------- Post added at 02:47 PM ---------- Previous post was at 02:42 PM ----------
AndroidDeveloperLB said:
So there is no definite conclusion? So my guess is that for Android it's too early to see difference between normal code and Lambda.
Click to expand...
Click to collapse
:good:
@sylsau thanks bro nice guide :good:
junaidshahidcom said:
such a nice post, i am studying the java but it is totally different why can you please explain what the java in book is different the java in applications??
Regards Junaid Shahid
---------- Post added at 02:47 PM ---------- Previous post was at 02:42 PM ----------
:good:
Click to expand...
Click to collapse
They are almost the same. The pure Java is still there, but some classes do not exist or have less functions, because Android is a mobile OS.
There is just another layer of the framework itself, that you need to learn, when developing for Android.
Thanks For Elaburation
AndroidDeveloperLB said:
They are almost the same. The pure Java is still there, but some classes do not exist or have less functions, because Android is a mobile OS.
There is just another layer of the framework itself, that you need to learn, when developing for Android.
Click to expand...
Click to collapse
Can you suggest me how to become a good developed of Java Along Android?
junaidshahidcom said:
Can you suggest me how to become a good developed of Java Along Android?
Click to expand...
Click to collapse
Learn both (first Java of course).
You can watch "the new boston" videos to get started:
https://thenewboston.com/videos.php
You can also read a lot on Google's website, but only after you are good with Java.
awesome
AndroidDeveloperLB said:
Learn both (first Java of course).
You can watch "the new boston" videos to get started:
https://thenewboston.com/videos.php
You can also read a lot on Google's website, but only after you are good with Java.
Click to expand...
Click to collapse
the website you referred is awesome, i will try to learn all programming languages from here <3
regards Junaid Shaid
princevirus said:
@sylsau thanks bro nice guide :good:
Click to expand...
Click to collapse
No problem. I'm going to publish more tutorials very soon
Thanks.
Android小楼阁-QQ群 439637151
来自搭载Android 2.3 GingerBread的华为Y220-T10
Hello,
I made a new tutorial available on XDA Forum. It shows you how to implement a Navigation Drawer with a Toolbar on Android.
Don't hesitate to discover it : http://forum.xda-developers.com/android/software/tutorial-implement-navigation-drawer-t3388990
Sylvain
sylsau said:
Hello,
I made a new tutorial available on XDA Forum. It shows you how to implement a Navigation Drawer with a Toolbar on Android.
Don't hesitate to discover it : http://forum.xda-developers.com/android/software/tutorial-implement-navigation-drawer-t3388990
Sylvain
Click to expand...
Click to collapse
hi, can that commit can help to use java 8 on M?
https://github.com/kogone/android_build/commit/ac67b54797f06b67a1ce0e39aa8528dbffac3b92