Question

I have implemented custom Android SurfaceView and meet error when I add callback for it.

Here is my code for class SurfaceView:

public class AndroidSurface extends SurfaceView {

    public SurfaceHolder holder;

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

        holder = getHolder();
        holder.addCallback(new SurfaceHolder.Callback() {

            public void surfaceChanged(SurfaceHolder holder, int format,
                    int width, int height) {
                // TODO Auto-generated method stub

            }

            public void surfaceCreated(SurfaceHolder holder) {
                // TODO Auto-generated method stub

            }

            public void surfaceDestroyed(SurfaceHolder holder) {
                // TODO Auto-generated method stub

            }


        });
    }
}

When I add this view to layout.xml, for example :

<com.app.AndroidSurface
        android:id="@+id/surfaceView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_above="@+id/rightBtn"
        android:layout_alignParentLeft="true"
        android:layout_alignParentRight="true"
        android:layout_below="@+id/textView1" />

I will met error when show in Graphical Layout : failed to instantiate. (at Plugin : com.android.ide.eclipse.adt) and when run this project, I will have exception. When view in LogCat, I see that Java Null Point Exception.

The strange thing is : if I remove holder.addCallback(new SurfaceHolder.Callback() {... no error met.

This looks strange too me, please tell me how to fixed this.

@ Edited : and the problem because when I getHolder, it doesn’t return surface holder, so holder is null, I don’t know why.

Thanks 🙂

Answer 1

You should check your context and make sure you are doing things in the correct order with respect to your lifecycle. Check out this post surfaceView.getHolder not returning SurfaceHolder