I am using surface view to show some graphics, the problem is that there is a flickering effect when I am moving the figure in the screen, I understand that this is due to double buffering problem, even though I went through many posts, I am unable to fix the problem, please take a look at my code and help me get this fixed.
public class CustomSurfaceView extends SurfaceView implements Runnable{
Thread mThread = null;
SurfaceHolder mSurfaceHolder;
volatile boolean mRunning = false;
Bitmap mBitmap;
boolean mTouched;
float mTouched_x,mTouched_y;
Context mContext;
float mCurrentPosOfRect1x1,mCurrentPosOfRect1y1,mCurrentPosOfRect1x2,mCurrentPosOfRect1y2;
float mCurrentPosOfRect2x1,mCurrentPosOfRect2y1,mCurrentPosOfRect2x2,mCurrentPosOfRect2y2;
private Paint mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
boolean isInitialized = false;
/**
* Constructor..
*/
public CustomSurfaceView(Context context) {
super(context);
mSurfaceHolder = getHolder();
mBitmap = BitmapFactory.decodeResource(getResources(), R.drawable.ic_launcher);
mContext = context;
mCurrentPosOfRect1x1 = 100;
mCurrentPosOfRect1y1 = 100;
mCurrentPosOfRect1x2 = 300;
mCurrentPosOfRect1y2 = 300;
mCurrentPosOfRect2x1 = 300;
mCurrentPosOfRect2y1 = 300;
mCurrentPosOfRect2x2 = 500;
mCurrentPosOfRect2y2 = 500;
}
public void onResumeMySurfaceView(){
mRunning = true;
mThread = new Thread(this);
mThread.start();
}
public void onPauseMySurfaceView(){
boolean retry = true;
mRunning = false;
while(retry){
try {
mThread.join();
retry = false;
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
@Override
public void run() {
while(mRunning){
if(mSurfaceHolder.getSurface().isValid()){
Canvas canvas = mSurfaceHolder.lockCanvas();
//... actual drawing on canvas
mPaint.setStyle(Paint.Style.STROKE);
if(mTouched){
canvas.drawColor(Color.BLACK);
mPaint.setColor(Color.BLACK);
mPaint.setStrokeWidth(3);
mPaint.setStrokeWidth(0);
mPaint.setColor(Color.CYAN);
//Left,top
//Right bottom.
if(!isInitialized){
canvas.drawRect(mCurrentPosOfRect1x1, mCurrentPosOfRect1y1,mCurrentPosOfRect1x2, mCurrentPosOfRect1y2,mPaint);
isInitialized = true;
}
mPaint.setColor(Color.BLACK);
mPaint.setStrokeWidth(3);
mPaint.setStrokeWidth(0);
mPaint.setColor(Color.BLUE);
//Left,top
//Right bottom.
if(!isInitialized){
canvas.drawRect(mCurrentPosOfRect2x1, mCurrentPosOfRect2y1,mCurrentPosOfRect2x2, mCurrentPosOfRect2y2,mPaint);
isInitialized = true;
}
if(isInitialized){
//Check whether the touch points are inside the rectangle & then move...
if((mTouched_x>mCurrentPosOfRect1x1) && (mTouched_x<mCurrentPosOfRect1x2) && (mTouched_y>mCurrentPosOfRect1y1) && (mTouched_y<mCurrentPosOfRect1y2)){
mCurrentPosOfRect1x1 = mTouched_x-100;
mCurrentPosOfRect1x2 = mTouched_x+100;
mCurrentPosOfRect1y1 = mTouched_y-100;
mCurrentPosOfRect1y2 = mTouched_y+100;
}else if((mTouched_x>mCurrentPosOfRect2x1) && (mTouched_x<mCurrentPosOfRect2x2) && (mTouched_y>mCurrentPosOfRect2y1) && (mTouched_y<mCurrentPosOfRect2y2)){
mCurrentPosOfRect2x1 = mTouched_x-100;
mCurrentPosOfRect2x2 = mTouched_x+100;
mCurrentPosOfRect2y1 = mTouched_y-100;
mCurrentPosOfRect2y2 = mTouched_y+100;
}
}
canvas.drawRect(mCurrentPosOfRect1x1, mCurrentPosOfRect1y1,mCurrentPosOfRect1x2, mCurrentPosOfRect1y2, mPaint);
mPaint.setColor(Color.RED);
canvas.drawRect(mCurrentPosOfRect2x1, mCurrentPosOfRect2y1,mCurrentPosOfRect2x2, mCurrentPosOfRect2y2, mPaint);
mPaint.setColor(Color.BLUE);
Paint paint = new Paint() {
{
setStyle(Paint.Style.STROKE);
setStrokeCap(Paint.Cap.ROUND);
setStrokeWidth(3.0f);
setAntiAlias(true);
}
};
paint.setColor(Color.YELLOW);
final Path path = new Path();
final float x1 = mCurrentPosOfRect1x1+ 100;
final float y1 = mCurrentPosOfRect1y1 + 100;
final float x3 = (mCurrentPosOfRect2x1+ 100) ;
final float y3 = (mCurrentPosOfRect2y1 + 100);
final float x2 = (x1 +200);
final float y2 = (y1 -100);
final float x4 = (x3-100);
final float y4 = (y3+200);
path.moveTo(x1, y1);
path.cubicTo(x2,y2,x4,y4,x3,y3);
canvas.drawPath(path, paint);
}
mSurfaceHolder.unlockCanvasAndPost(canvas);
}
}
}
@Override
public boolean onTouchEvent(MotionEvent event){
mTouched_x = event.getX();
mTouched_y = event.getY();
int action = event.getAction();
switch(action){
case MotionEvent.ACTION_DOWN:
mTouched = true;
break;
case MotionEvent.ACTION_MOVE:
mTouched = true;
break;
case MotionEvent.ACTION_UP:
mTouched = false;
break;
case MotionEvent.ACTION_CANCEL:
mTouched = false;
break;
case MotionEvent.ACTION_OUTSIDE:
mTouched = false;
break;
default:
}
return true; //processed
}
}
If you call lockCanvas(), you need to draw on every pixel in the dirty rect. Since you're calling it without a dirty rect, that means updating every pixel on the Canvas.
I believe the problem with your code is that, when mTouched is false, you're not drawing anything at all. Because the Surface is double- or triple-buffered, you're re-displaying the contents of a previous frame, which is going to cause a vibration effect.
I think all you need to do is move the test for mTouched before the lockCanvas() call, so you don't flip the buffers if you're not going to draw anything.
You may want to look through the SurfaceView lifecycle appendix in the graphics architecture doc if you haven't seen it before, as the thread management sometimes yields surprises.