Question

I’m developing a live wallpaper, and I have a problem that has been bugging me for a while. My live wallpaper crashes when it’s turned into landscape and then back to portrait several times in a row.
The LogCat shows the following error:

FATAL EXCEPTION: main
java.lang.IllegalArgumentException
at android.view.Surface.unlockCanvasAndPost(Native >Method)
at com.android.internal.view.BaseSurfaceHolder.unlockCanvasAndPost(BaseSurfaceHolder.java:215)
at livewallpaper.LiveWallpaper$CatWallEngine.draw(LiveWallpaper.java:167)….

This is the code:

    public void draw() {
        SurfaceHolder holder = getSurfaceHolder();
        Canvas c = null;
        paint = new Paint();
        try {
            c = holder.lockCanvas();
            if (c != null ) {
                //drawing code goes here
            }

        } finally {
            if (c != null) {
                holder.unlockCanvasAndPost(c);
            }
        }

        mHandler.removeCallbacks(mUpdateDisplay);
        if (mVisible) {
            mHandler.postDelayed(mUpdateDisplay, 50);
        }

The line 167 is the holder.unlockCanvasAndPost(c); line.
I’ve read elsewhere that trying to unlock the canvas that is not locked might cause this error, but I’ve checked that and that’s not the problem: canvas gets locked every time before trying to unlock it.

Answer 1

After I added the try/catch block inside my ‘finally’ block, the live wallpaper stopped crashing.
My ‘finally’ block looks like this now:

            try {
                if (c != null) {
                    holder.unlockCanvasAndPost(c);
                }

            } catch (IllegalArgumentException exception) {
                exception.printStackTrace();
            }