Develop Reference

How to create ECG animation on Android Application

I coded an android application which is measuring heart rate from camera input. I needed to desing an ECG animation to the application. I know that ECG isn't related. But I'll try to show the sign according to heart rate. Which method do I need to use? Drawing animation into a View object from layout or Drawing graphics directly to a Canvas. And if you give some clues I'll be very appreciated.

To do real time graphing of ECG data...which is what I am coding right now, you need to create a custom view. Then in the onDraw method you use your canvas to draw a bitmap. Then inside the custom I also implement a Runnable that paints the line using drawline, and then invalidates(). I'd show you code but its proprietary since everything I found did not measure up to the speeds I had to graph.

It depends how real-time you need your data. If a lower framerate is sufficient, then I would recommended subclassing the View class and overriding the onDraw method. From there you can draw directly onto the canvas. Just make sure to call invalidate on the view after your data changes to make sure onDraw gets called.
If a faster framerate is required, then you probably want to use a SurfaceView. Google has a Lunar Lander example that does a good job of that. But note some bugs have been found in the example, so use it as a guide not as law.
Lunar Lander:
http://developer.android.com/resources/samples/LunarLander/index.html

The proper way to create a 2d android game

After getting help with starting android pong, I realized that I painted myself into a corner.
For reference on the code(Its long) and advice, here is a link to the last thread Updating player score in an android game
Basically the frame rate is halved when i touch the screen. I think it is due to updating everything or drawing on the canvas. This also lends itself to bad communication between the pieces of the application(the view, frame, and oncreate). Is there a recommended way to create an android 2d game? This is based off the lunar landing game and it seemed fine but when i tried to recreate it , it seemed much worse. I could not find a lot of resource on a best practice for drawing and so far this seems a bit discouraging.
So in short
How would you modify the code posted in the link to improve performance? Or did I paint myself into a poorly made corner, and it is time to start a new? If so , how?
Thanks

You don't need invalidate() in onTouch because you are already running a frame animation by the additional thread.
Try to define all the fixed values/variables in the constructor of the SurfaceView or in onSizeChanged() where you know the size of the canvas and bitmaps loaded, so not to make any unneccesary variable creation, requests or calcualtions in onDraw, onTouch or other methods to handle game logic, otherwise it will slow down.

How to animate in Android Canvas?

I want to draw something at about 30 frames per seconds on Android Canvas or other convenient object for this purpose. In my application different graphic objects are drawn and if any of the graphic object is touched, the graphic object changes its shape. I looked at the
onDraw(Canvas canvas) callback of View subclass but calling invalidate() does not help here: first I cannot control the frame rate and second if the objects are moving too fast, the motion appears jerky.

I personally dislike Android's built-in Animation classes, so I tend to do all animations with Canvas by hand. I have found the most luck with creating a list of the images you want to use in your animation and then an int variable to store the current "frame" you are on. To advance the frame, I create a thread that sleeps for, say, 30 ms and then update the frame variable accordingly. Then in whatever update handler you are using, you can just create a switch statement or something of the like, and draw the respective frame.
It may seem like a lot of work, but it really isn't. Shove it all into a class and you will love yourself for many animations to come.

How to do animations in Android chess game

I'm developing chess game for Android (androidchess.appspot.com). If I want to add animations, should I use custom View extending Canvas (I do this now), or custom View extending SurfaceView?

I haven't tried using a View to extend Canvas, but for my game I'm using the same method as the LunarLander example game:
public class CustomView extends SurfaceView implements SurfaceHolder.Callback
The usefulness of this is that it gives you handles for SurfaceHolder (so you can call up the canvas which is drawn to the screen), and the callbacks for surfaceCreated, surfaceChanged and surfaceDestroyed. That lets you do things like drawing a custom animation as soon as the surface is available or make sure that you don't try to draw to the canvas after it has been deactivated. Looking through LunarLander should show you how to use these properly.
Edit: I remembered another reason why using a SurfaceHolder was useful. This is because, as I mentioned above, it lets you get direct access to the canvas which is drawn to the screen. With a SurfaceHolder this is done not by overriding onDraw but by using something like Canvas canvas = mSurfaceHolder.lockCanvas(). (See LunarLander for exact syntax). The reason this is important is because it lets you control exactly when the drawing happens. If you can only work by overriding onDraw(), then the drawing doesn't happen until your program reaches a 'waiting' phase. In other words, you can't use invalidate() and onDraw() in a loop because the drawing won't happen until the loop finishes. And since you're likely to use loops for things like drawing a piece moving across the screen, this becomes a problem.
Note: It may be possible to avoid this problem by using multiple threads. I simply haven't tried that since it isn't required for my game; the only animation is has is fixed-length animations in response to user input rather than something continuously moving in the background, so I haven't experimented with multiple threads yet.

Making a draw/paint app

I'd like to include a simple draw feature on my app. A friend told me I can't use canvas because I need to control the frame buffer and not redraw the entire screen every for every frame. He suggested I find a openGL 2d engine. I've searched around and I've only found Rokon which doesn't have any documentation and the examples aren't quite what I need.
Any suggestions?

I don't really understand what the problem is?
If you simply wish to redraw some portion of the canvas you can use invalidate(rect).
http://developer.android.com/reference/android/view/View.html#invalidate()

Just create a custom veiw by extending the view class. in this custome view override the onDraw method. Android itself takes care of the pixels that have been changed and calling invalidate only refreshes the pixels that have been marked dirty