java.lang.IllegalStateException: Surface has already been released.

01-03 11:14:09.312 26780-26808/ddolcatmaster.codeforgame E/AndroidRuntime: FATAL EXCEPTION: Thread-3
    Process: ddolcatmaster.codeforgame, PID: 26780
    java.lang.IllegalStateException: Surface has already been released.
        at android.view.Surface.checkNotReleasedLocked(Surface.java:564)
        at android.view.Surface.unlockCanvasAndPost(Surface.java:327)
        at android.view.SurfaceView$3.unlockCanvasAndPost(SurfaceView.java:1114)
        at ddolcatmaster.codeforgame.GThread.run(GThread.java:34)

@Override
public void run() {
super.run();

    while (true){
        Canvas canvas = null;
        canvas = mHolder.lockCanvas(); 
        try{
synchronized (mHolder){ //다른 스레드와 동기화 유지
                canvas.drawBitmap(imageBack,0,0,null);
            }
        }catch (Exception e){
            e.printStackTrace();
        }finally {
mHolder.unlockCanvasAndPost(canvas); 
        }
    }
}

Surface가 이미 Released 되었기 때문에 조건문을 추가해야한다.

@Override
public void run() {
super.run();

    //스레드로 canvas에 출력
    while (true){
        Canvas canvas = null;
        canvas = mHolder.lockCanvas(); //캔버스를 잠그고
        try{
synchronized (mHolder){ //다른 스레드와 동기화 유지
                canvas.drawBitmap(imageBack,0,0,null); // 내부 버퍼에 그린다.
            }
        }catch (Exception e){
            e.printStackTrace();
        }finally {
if(canvas != null)
                mHolder.unlockCanvasAndPost(canvas); //버퍼에 그려진 것을 view로 보낸다.
        }
    }
}