Touch to move Bitmap inside a custom View

Refer to the article Detect Touch Event, test on Custom View. Modify to add a Bitmap in the custom view, if user touch the View over the bitmap, it will be moved accordingly.

package com.TestSingleTouch;

import android.app.Activity;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.os.Bundle;
import android.view.MotionEvent;
import android.view.View;

public class TestSingleTouch extends Activity {
 
 
 public class TouchView extends View {
  
  private Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);
  private float x, y;
  boolean touching = false;
  
  Bitmap bm = BitmapFactory.decodeResource(
      getResources(),
      R.drawable.ic_launcher);
  int bm_x = 0;
  int bm_y = 0;
  int bm_w = bm.getWidth();
  int bm_h = bm.getHeight();
  int bm_offsetx;
  int bm_offsety;
  boolean dm_touched = false;
  
  
  public TouchView(Context context) {
   
   super(context);
   // TODO Auto-generated constructor stub 
   
  }
  
  @Override
  protected void onDraw(Canvas canvas) {
   // TODO Auto-generated method stub
   paint.setStyle(Paint.Style.STROKE);
   paint.setStrokeWidth(1);
   paint.setColor(Color.WHITE);
   
   if(touching){
    canvas.drawRect(x, y, x+bm_w, y+bm_h, paint);
   }
   
   canvas.drawBitmap(bm, bm_x, bm_y, paint);
  }
  
  @Override
  protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
   // TODO Auto-generated method stub
   setMeasuredDimension(MeasureSpec.getSize(widthMeasureSpec),
     MeasureSpec.getSize(heightMeasureSpec)); 
  }
  
  @Override
  
  public boolean onTouchEvent(MotionEvent event) {
   // TODO Auto-generated method stub
   int action = event.getAction();
   switch(action){
   case MotionEvent.ACTION_MOVE:
    x = event.getX();
    y = event.getY();
    touching = true;

    if(dm_touched){
     bm_x = (int)x - bm_offsetx;
     bm_y = (int)y - bm_offsety;
    }
    
    break; 
   case MotionEvent.ACTION_DOWN:
    x = event.getX();
    y = event.getY();
    touching = true;
    
    //check if bm touched
    if((x > bm_x)
     && (x < bm_x+bm_w)
     && (y > bm_y)
     && (y < bm_y+bm_h)){
     bm_offsetx = (int)x - bm_x;
     bm_offsety = (int)y - bm_y;
     dm_touched = true;
    }
    
    break; 
   case MotionEvent.ACTION_UP:
   default:
    dm_touched = false;
    touching = false; 
   }

   invalidate();
   return true; 
  } 
 }
 
 /** Called when the activity is first created. */
 @Override
 public void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(new TouchView(this)); 
  
 }
}

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