Develop Reference

Drawing in a SurfaceView - canvas is null when calling holder.lockCanvas() in surfaceCreated()

I found a number of postings related to my question but none of them solved it. I'm trying it again. Hopefully my example is simple enough and I haven't forgotten anything crucial.
I have a Fragment and an inner class CameraPreview, derived from SurfaceView and implementing SurfaceHolder.Callback. What I want achieve is drawing on top of the camera preview that's displayed full-screen through CameraPreview.
I thought calling canvas = holder.lockCanvas() in surfaceCreated() would give me a Canvas for later drawing but mCanvas is always null if called after setPreviewDisplay() and startPreview(). If try to create the canvas before those two calls, I get a canvas but the app crashes immediately after.
Can someone explain why?
public class CameraFragment extends Fragment {
final static String TAG = "CameraFragment";
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_native_camera, container, false);
// Create our Preview view and set it as the content of our activity.
safeCameraOpenInView(view);
return view;
}
public void safeCameraOpenInView(View view) {
FrameLayout preview;
Camera camera = null;
try {
camera = Camera.open();
} catch (Exception e) {
e.printStackTrace();
}
if (camera != null) {
mPreview = new CameraPreview(getActivity().getApplicationContext(), camera);
if (view.findViewById(R.id.camera_preview) != null) {
preview = (FrameLayout) view.findViewById(R.id.camera_preview);
preview.addView(mPreview);
Log.d(TAG, "view found and set");
} else Log.d(TAG, "FrameLayout is null");
}
}
class CameraPreview extends SurfaceView implements SurfaceHolder.Callback {
private Camera mCamera;
private Canvas mCanvas;
public CameraPreview(Context context, Camera camera) {
super(context);
// not sure the following is necessary
setWillNotDraw(false);
// do camera initialisation etc.
mCamera = camera;
// ...
}
public void surfaceCreated(SurfaceHolder holder) {
// here's the problem: If I initialize the canvas
// before setting the preview display and start previewing
// I get a canvas but the app crashes immediately after
// If I request the canvas afterwards it's simply null
mCamera.setPreviewDisplay(holder);
mCamera.startpreview();
mCanvas = holder.lockCanvas();
// mCanvas is null
Log.d(TAG, "canvas: " + mCanvas);
}
}
}

Android SurfaceView with drawBitmap(Matrix) leaves blinking ghost image

To preface, I'm probably going to work with Views instead of SurfaceView given this weird interaction, but my curiosity is getting the better of me and I want to know what's going on.
So I have a matrix class variable. I run matrix.setTranslate() once, and every other frame I say matrix.setTranslate(). After this I call canvas.drawBitmap(, matrix, null). After 100 frames, I stop drawing the bitmap.
Here's the code:
public void onDraw(Canvas canvas) {
super.onDraw(canvas);
// matrix = new Matrix(); //Doesn't matter if I add this.
// matrix.reset(); //This doesn't matter either.
if (!once) {
matrix.setTranslate(100, 100);
} else {
matrix.setTranslate(800,800);
}
once = true;
if (++timer < 100) {
canvas.drawBitmap(ball, matrix, null);
}
}
What I expect to happen: Three possibilities.
Only the bottom right bitmap is visible since the entire screen was invalidated
Both bitmaps are visible because SurfaceView was smart with the dirty rectangle
Nothing is shown because nothing was drawn.
What actually happens: The top left bitmap blinks, bottom right bitmap displays solidly.
I'm pretty sure I have all of my bases covered:
All class variables are properly set in the constructor.
SurfaceView.onDraw() is called every 33 millis in its own thread.
Thread calls lockCanvas, then onDraw, then unlockCanvasAndPost
So, what's going on here? And bonus question, do these ghost images consume any extra resources and how can I clear them?
Rest of the code, mostly boilerplate:
public class FullscreenActivity extends Activity {
GameSurface ball;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
ball = new GameSurface(this);
setContentView(ball);
}
}
class GameSurface extends SurfaceView implements SurfaceHolder.Callback {
GameThread thread;
boolean once = false;
Bitmap ball;
Matrix matrix;
int timer = 0;
public GameSurface(Context context) {
super(context);
ball = BitmapFactory.decodeResource(getResources(),R.drawable.football);
matrix = new Matrix();
getHolder().addCallback(this);
setFocusable(true);
}
#Override
public void onDraw(Canvas canvas) {
super.onDraw(canvas);
// matrix = new Matrix(); //Doesn't matter if I add this.
// matrix.reset(); //This doesn't matter either.
if (!once) {
matrix.setTranslate(100, 100);
} else {
matrix.setTranslate(800,800);
}
//matrix.postRotate(timer); //For even more weirdness...
once = true;
if (++timer < 100) {
canvas.drawBitmap(ball, matrix, null);
}
}
#Override
public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
}
#Override
public void surfaceCreated(SurfaceHolder holder) {
thread = new GameThread(getHolder(), this);
thread.setRunning(true);
thread.start();
}
#Override
public void surfaceDestroyed(SurfaceHolder holder) {
}
class GameThread extends Thread {
private SurfaceHolder surfaceHolder;
private GameSurface gameView;
private boolean run = false;
public GameThread(SurfaceHolder surfaceHolder, GameSurface gameView) {
this.surfaceHolder = surfaceHolder;
this.gameView = gameView;
}
public void setRunning(boolean run) {
this.run = run;
}
#Override
public void run() {
Canvas c;
while (run) {
c = null;
try {
Thread.sleep(33);
}
catch(InterruptedException e) {}
try {
c = surfaceHolder.lockCanvas();
synchronized (surfaceHolder) {
gameView.onDraw(c);
}
} finally {
if (c != null) {
surfaceHolder.unlockCanvasAndPost(c);
}
}
}
}
}
}

draw an android.media.Image to a surface

I have this android application.
It use a SurfaceView, from where I get the Surface through the SurfaceHolder.
It also use ExoPlayer to stream videos. However I have instantiated an ImageReader, getting its Surface and passing to the ExoPlayer.
Now, I am in the ImageReader.OnImageAvailableListener#onImageAvailable and I access the latest Image.
I want to manipulate the Image and send the new data to the "SurfaceView" Surface.
How can I "draw" an android.media.Image to an android.view.Surface ?

The question is not clear to me.
The way to get android.media.Image is by the Camera2 API, and there you can provide a surface and the "camera" will draw over it. Please refer to Camera2Video example
Another way to get the Image object is from ImageReader (while decoding video for example). In this case you want to draw the image, but you can not provide a surface to the ImageReader(there is an internal surface that is not displayed). In this case you can draw the Image on a SurfaceView.
Assuming this is the case, you need to convert an Image to a Bitmap objects.
You have discussion about how perform this here

Possible duplicate of: how to draw image on surfaceview android
First get your canvas by using lockCanvas() (see here), second get your image and make it a drawable using:
my_bitmap = Bitmap.createBitmap(
MediaStore.Images.Media.getBitmap(getContentResolver(), uri),
0,0,90, 90);
drawable=new BitmapDrawable(my_bitmap);
After that you can draw the drawable to the locked canvas and use unlockCanvasAndPost (Canvas canvas) to post the updated canvas back to the surfaceview.

here is the answer for your question.
MainActivity.java
public class MainActivity extends Activity {
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
mySurfaceView mySurfaceView = new mySurfaceView(getApplicationContext());
setContentView(mySurfaceView);
}
}
mySurfaceView.java
public class mySurfaceView extends SurfaceView implements
SurfaceHolder.Callback {
private TutorialThread _thread;
public mySurfaceView(Context context) {
super(context);
getHolder().addCallback(this);
_thread = new TutorialThread(getHolder(), this);
}
#Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
Bitmap _scratch = BitmapFactory.decodeResource(getResources(),
R.drawable.icon);
canvas.drawColor(Color.BLACK);
canvas.drawBitmap(_scratch, 10, 10, null);
}
public void surfaceChanged(SurfaceHolder arg0, int arg1, int arg2, int arg3) {
}
public void surfaceCreated(SurfaceHolder arg0) {
_thread.setRunning(true);
_thread.start();
}
public void surfaceDestroyed(SurfaceHolder arg0) {
boolean retry = true;
_thread.setRunning(false);
while (retry) {
try {
_thread.join();
retry = false;
} catch (InterruptedException e) {
}
}
}
class TutorialThread extends Thread {
private SurfaceHolder _surfaceHolder;
private mySurfaceView _panel;
private boolean _run = false;
public TutorialThread(SurfaceHolder surfaceHolder, mySurfaceView panel) {
_surfaceHolder = surfaceHolder;
_panel = panel;
}
public void setRunning(boolean run) {
_run = run;
}
#Override
public void run() {
Canvas c;
while (_run) {
c = null;
try {
c = _surfaceHolder.lockCanvas(null);
synchronized (_surfaceHolder) {
_panel.onDraw(c);
}
} finally {
if (c != null) {
_surfaceHolder.unlockCanvasAndPost(c);
}
}
}
}
}
}

Is their any way to do Frame by Frame Animation in canvas ..?

For normal Activity with the help of ImageView we are able to attain Frame Animation ("Through some online tutorial i done that")
img = (ImageView) findViewById(R.id.myimage);
img.setBackgroundResource(R.drawable.loadimage);
AnimationDrawable frameAnimation = (AnimationDrawable) img.getBackground();
frameAnimation.start();
but here in Canvas i'm using Bitmap to get an image to the view, their i'm stuck..
Resources res = getResources();
Bitmap bitmap = BitmapFactory.decodeResource(res, R.drawable.loadimage);
is their any way to do frame animation in canvas..?

You can create an animated custom view using SurfaceView with a Thread to schedule the animation times properly.
The idea is to extend from SurfaceView, get the Canvas from the SurfaceHolder, draw on it, post the draw on the screen, and repeat (done in a background thread). A basic example:
public class CustomView extends SurfaceView implements Runnable {
Thread animationThread = null;
SurfaceHolder holder;
volatile boolean running = false;
public CustomView(Context context) {
super(context);
holder = this.getHolder();
}
// called from Activity's onResume() to start the thread
public void resume() {
running = true;
animationThread = new Thread(this);
animationThread.start();
}
// called from Activity's onPause() to end the thread
public void pause() {
running = false;
while(true) {
try {
animationThread.join();
break;
} catch (InterruptedException e) { }
}
}
// run until pause() is called
#Override
public void run() {
while(running) {
if(!holder.getSurface().isValid())
continue;
Canvas canvas = holder.lockCanvas();
// your drawing logic goes here:
// - calculate the time of the frame
// - draw a different bitmap each time ...
canvas.drawBitmap(...)
holder.unlockCanvasAndPost(canvas);
}
}
}
To handle the size of the view, you would need to override onMeasure() and onSizeChanged().
For a better understanding of how this works:
http://blog.infrared5.com/2011/06/android-graphics-and-animation-part-i/
http://blog.infrared5.com/2011/07/android-graphics-and-animation-part-ii-animation/
http://developer.android.com/reference/android/view/SurfaceView.html

Initializing SurfaceView with a Drawable

I'd like to open up a SurfaceView with a icon placed in the center of the screen when an application is first started. I'm evoking icon creation using an implementation of SurfaceHolder.Callback to track when the 'Canvas' object is ready. My question is is there a better way? Are there less cumbersome methods of starting a SurfaceView with some Drawables loaded on creation without having to resort to placing draw logic within a callback object?
Here's my code for reference. First the object which does drawing:
public class CanvasDraw{
protected final SurfaceHolder mHolder;
protected final Drawable mDrawable;
public interface DrawLogic{
void draw(Rect _surface);
}
public CanvasDraw(SurfaceView _view, Drawable _drawable){
mHolder = _view.getHolder();
mDrawable = _drawable;
}
public void draw(DrawLogic _logic){
Canvas canvas = null;
try{
canvas = mHolder.lockCanvas();
if( canvas != null ){
Log.i("DRAWABLE", "Drawing " + mDrawable.toString());
_logic.draw( mHolder.getSurfaceFrame() );
mDrawable.draw(canvas);
}
else{
Log.i("DRAWABLE", "Canvas null valued");
}
}
finally{
if( canvas != null ){
mHolder.unlockCanvasAndPost(canvas);
}
}
}
}
and then my private callback object:
private class DrawOnceCallback implements SurfaceHolder.Callback {
private final SurfaceHolder mHolder;
public DrawOnceCallback(SurfaceHolder _holder ){
mHolder = _holder;
mHolder.addCallback(this);
}
#Override
public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {}
#Override
public void surfaceCreated(SurfaceHolder holder) {
Log.i("SURFACEHOLDER","Surface created. Canvas available.");
mDrawTiles.draw( new CanvasDraw.DrawLogic(){
#Override
public void draw(Rect _surface) {
mTiles.setBounds(
_surface.centerX() - mDrawWidth/2,
_surface.centerY() - mDrawHeight/2,
_surface.centerX() + mDrawHeight/2,
_surface.centerY() + mDrawHeight/2);
}
});
mHolder.removeCallback(this);
}
#Override
public void surfaceDestroyed(SurfaceHolder holder) {Log.i("SURFACEHOLDER","Surface destroyed.");}
}

I did something like this simply by assigning the image I wanted to a view in the layout XML file. If you've got to wait until your canvas and all that is ready anyways why not just use a default property? My opening splash screen was just a view with
android:background="#drawable/splash"
added to its layout.