Auf eingeladenem Bild zeichnen

public class Feldbuch extends ActionBarActivity  {
    
    ImageView bild;
    File Pfad;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, WindowManager.LayoutParams.FLAG_FULLSCREEN);
        setContentView(new Zeichenfunktion(this));         
//        setContentView(R.layout.activity_feldbuch);
        
        bild = (ImageView) findViewById(R.id.imageView1);
    }
    



    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.feldbuch, menu);
        return true;
    }

public class Zeichenfunktion extends View implements OnTouchListener
{
  Bitmap bitmap;
  Canvas bitmapCanvas;
  ImageView bild;
  File Pfad;

    boolean isInitialized;
    Paint paint = new Paint();

    public Zeichenfunktion(Feldbuch context)
    {
        super(context);
        setFocusable(true);
        setFocusableInTouchMode(true);

        this.setOnTouchListener(this);

        paint.setColor(Color.GREEN);
        paint.setAntiAlias(true);
        paint.setStyle(Style.FILL_AND_STROKE);
        
        isInitialized = false;
    }


    private void init()
    {
        bitmap = Bitmap.createBitmap(getWidth(), getHeight(), Bitmap.Config.RGB_565);
        
        bitmapCanvas = new Canvas();
        bitmapCanvas.setBitmap(bitmap);
        bitmapCanvas.drawColor(Color.TRANSPARENT);
        
        isInitialized = true;

    }
    
    @Override
    public void onDraw(Canvas canvas)
    {
        if (!isInitialized)
            init();
        
        canvas.drawBitmap(bitmap, 0, 0, paint); 
    }

    public boolean onTouch(View view, MotionEvent event)
    {
        bitmapCanvas.drawCircle(event.getX(), event.getY(), 5, paint);

        
        invalidate();
        return true;
    }




public boolean onOptionsItemSelected(MenuItem item) {
//    // Handle action bar item clicks here. The action bar will
//    // automatically handle clicks on the Home/Up button, so long
//    // as you specify a parent activity in AndroidManifest.xml.
//    int id = item.getItemId();
//    if (id == R.id.action_settings) {
//        return true;
//    }
//    return super.onOptionsItemSelected(item);      
    }
    if (item.toString().equals("Löschen"));
    {
        
    }
    if (item.toString().equals("Speichern"));
    {
        
    }
    if (item.toString().equals("Laden"));
    {
    Pfad = new File("/mnt/sdcard/external_sdcard/Feldbuch/Riss.jpg");    
    bild.setImageURI(Uri.fromFile(Pfad));    
    }
    return true;
    }
}