Question

Friends,

i want to make a seamless background as a custom view component.

the problem i figured out during debugging,

the first time i call invalidate() within the thread my onDraw callback method is called.
The other times my thread is calling invalidate() the onDraw callback method is not called.

so its just running over the invalidate() method , like it would not even exist.

The application displays the seamlessbackground png. But as static. it not gets updated.

I post all my code because the bug might be outside of the thread, where invalidate() is located or outside the onDraw method.

apprechate any kind of help! so THX

              public class MyBringBackSurface extends View implements Runnable {

Bitmap bitmapResource;
int leftFrameX, rightFrameX, startX, stopX, bitmapPixelWidth,
        bitmapPixelHight;
int pixelPerFrame = 10;
int framerate = 100;
int threadSleepTime;
int offsetYInPixel = 200;
Thread ourthread = null;
boolean isrunning = false;

Canvas c;

public MyBringBackSurface(Context context) {
    super(context);

    init();

}

public MyBringBackSurface(Context context, AttributeSet attrs) {
    super(context, attrs);

    init();

}

public MyBringBackSurface(Context context, AttributeSet attrs, int defStyle) {
    super(context, attrs, defStyle);

    init();

}

private void init() {


    // Set up Bitmap Resource

    bitmapResource = BitmapFactory.decodeResource(getResources(),
                    R.drawable.simelessbackground);


 //  c = new Canvas(bitmapResource);


    // Implementing leftFrameX and rightFrameX
    leftFrameX = 0;
    rightFrameX = bitmapResource.getWidth();

    // Calculating the Thread sleep time
    threadSleepTime = 1000 / framerate;



}

public void pause() { // destroy the currently running thread because
                        // anyways in the on resume will be created a
                        // new one again

    isrunning = false;
    while (true) {

        try { // goes through this thread until our thread died
            ourthread.join(); // Blocks the current Thread
                                // (Thread.currentThread()) until the
                                // receiver finishes its execution and
                                // dies.
        } catch (InterruptedException e) {

            e.printStackTrace();
        }
        break;
    }


}

public void resume() {

    isrunning = true;
    ourthread = new Thread(this);

    ourthread.start();

}

public void run() {

    while (isrunning) {

        try {
            Thread.sleep(threadSleepTime);
            // formula is 1000/ sleep time (here 5) = frame rate
        } catch (InterruptedException e) {

            e.printStackTrace();
        }

        invalidate();

        // Add pixelPerFrame and draw again
        leftFrameX = leftFrameX - pixelPerFrame;
        rightFrameX = rightFrameX - pixelPerFrame;

        // if picture is completely out of the screen, start over again
        if (leftFrameX <= -bitmapResource.getWidth()) {
            leftFrameX = 0;
            rightFrameX = bitmapResource.getWidth();
        }
    }
}

/**
 * Render the text
 * 
 * @see android.view.View#onDraw(android.graphics.Canvas)
 */
@Override
protected void onDraw(Canvas canvas) {
    super.onDraw(canvas);


    canvas.drawRGB(255, 255, 255);

    // Draw Rectangle 1250 pixel
    Rect rect1000 = new Rect();
    rect1000.set(0, 0, 1250, 20);
    Paint blue = new Paint();
    blue.setColor(Color.BLUE);
    canvas.drawRect(rect1000, blue);

    // Draw first Bitmap
    Rect rectBitmapSource = new Rect(0, 0, bitmapResource.getWidth(),
            bitmapResource.getHeight());
    Rect rectBitmapDestinationFirst = new Rect(leftFrameX, offsetYInPixel,
            rightFrameX, offsetYInPixel + bitmapResource.getHeight());
    canvas.drawBitmap(bitmapResource, rectBitmapSource,
            rectBitmapDestinationFirst, null);

    // Draw second Bitmap

    Rect rectBitmapDestinationSecond = new Rect(
            (leftFrameX + bitmapResource.getWidth()), offsetYInPixel,
            (rightFrameX + bitmapResource.getWidth()), offsetYInPixel
                    + bitmapResource.getHeight());
    canvas.drawBitmap(bitmapResource, rectBitmapSource,
            rectBitmapDestinationSecond, null);



}

}

Answer 1

I figured out the answer after going throught the googledocs.

if you want to invalidate a View from outside of the UI-Thread you have to use the
postinvalidate() command instead of invalidate().

Thats it. It will work like charme!!!