ドラッグで画像移動-Canvas

package com.androidGui;

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

public class AndroidGui extends Activity {
 /** Called when the activity is first created. */
 @Override
 public void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);

  setContentView(new SampleView(this));
 }

 private class SampleView extends View {

  private Paint mPaint;
  private float imageX;
  private float imageY;
  private Bitmap mBitmap;

  public SampleView(Context context) {
   super(context);
   // TODO 自動生成されたコンストラクター・スタブ
   mPaint = new Paint();
  }

  @Override
  protected void onDraw(Canvas canvas) {
   // 画像表示
   mBitmap = BitmapFactory.decodeResource(getResources(), R.drawable.icon);
   canvas.drawBitmap(mBitmap, imageX - mBitmap.getWidth() / 2, 
     imageY - mBitmap.getHeight() / 2, mPaint);
  }

  @Override
  public boolean onTouchEvent(MotionEvent event) {

   // 触る
   if (event.getAction() == MotionEvent.ACTION_DOWN) {
    imageX = event.getX();
    imageY = event.getY();
   }
   // 触ったままスライド
   else if (event.getAction() == MotionEvent.ACTION_MOVE) {
    imageX = event.getX();
    imageY = event.getY();
   }

   // 離す
   else if (event.getAction() == MotionEvent.ACTION_UP) {
    imageX = event.getX();
    imageY = event.getY();
   }

   // 再描画の指示
   invalidate();

   return true;
  }

 }
}

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