让图片跟着手指动【Android Demo】

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【PictureMoveDemoActivity.java】

package com.demo.picmove;

import android.app.Activity;
import android.os.Bundle;
import android.util.DisplayMetrics;
import android.util.Log;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.AbsoluteLayout;
import android.widget.ImageView;
import android.widget.Toast;

public class PictureMoveDemoActivity extends Activity {

// 声明存储屏幕宽高分辨率的对象
private int screenX, screenY;

private ImageView imageView;
// 初始化ImageView的默认位置
private int defaultX, defaultY;
// ImageView的宽高
private int imgWidth, imgHeight;

// 用来重新绘制手指所在位置图片的起始坐标
private float mX, mY;

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        // 取得屏幕对象
        DisplayMetrics dm = new DisplayMetrics();
        getWindowManager().getDefaultDisplay().getMetrics(dm);
        // 获取屏幕宽高
        screenX = dm.widthPixels;
        screenY = dm.heightPixels;

        // 设置图片大小为72*72
        imgWidth = 72;
        imgHeight = 72;
        // 设置图片资源
        imageView = (ImageView) findViewById(R.id.imageView);
        imageView.setImageResource(R.drawable.ic_launcher);
        // 获取图片宽高

        // 初始化按钮位置居中
        restoreButton();

        imageView.setOnClickListener(new OnClickListener() {
   public void onClick(View v) {
    restoreButton();
   }
  });
    }

    // 重写触控事件
    @Override
public boolean onTouchEvent(MotionEvent event) {
    // 获取手指触摸的坐标
    float x = event.getX();
    float y = event.getY();

    switch(event.getAction()) {
    case MotionEvent.ACTION_DOWN:
      pictureMove(x, y);
      break;
  case MotionEvent.ACTION_MOVE:
   pictureMove(x, y);
   break;
  case MotionEvent.ACTION_UP:
   pictureMove(x, y);
   break;
    }

  return true;
}

    // 关键：绘制移动后的图片的方法
    private void pictureMove(float x, float y) {
    mX = x - (imgWidth/2);
    mY = y - (imgHeight/2);

    // 判断mX/mY有没有超出屏幕范围
    if(mX>(screenX-imgWidth)) {
      mX = screenX - imgWidth;
    } else if(mX<0) {
      mX = 0;
    } else if(mY>(screenY-imgHeight)) {
      mY = screenY - imgHeight;
    } else if(mY<0) {
      mY = 0;
    }

    // 通过Log来查看图片的位置
    Log.e("img_xy = ", "(" + Float.toString(mX) + ", " + Float.toString(mY) + ")");

    // setLayoutParams
    imageView.setLayoutParams(
       new AbsoluteLayout.LayoutParams(imgWidth, imgHeight, (int) mX, (int) mY));

    }

private void restoreButton() {
    defaultX = (screenX - imgWidth)/2;
    defaultY = (screenY - imgHeight)/2;

    // 显示还原坐标的Toast
    String str = "(" + defaultX + ", " + defaultY + ")";
    makeToast(str, true);

    imageView.setLayoutParams(
       new AbsoluteLayout.LayoutParams(imgWidth, imgHeight, defaultX, defaultY));
    }

    private void makeToast(String str, boolean isLong) {
    if(isLong) {
      Toast.makeText(PictureMoveDemoActivity.this, str, Toast.LENGTH_LONG).show();
    } else {
      Toast.makeText(PictureMoveDemoActivity.this, str, Toast.LENGTH_SHORT).show();
    }
    }

}

【main.xml】

<?xml version="1.0" encoding="utf-8"?>
<AbsoluteLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent" >

</AbsoluteLayout>

【AndroidManifest.xml】

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.demo.picmove"
    android:versionCode="1"
    android:versionName="1.0" >

<uses-sdk android:minSdkVersion="15" />

</manifest>