android脚步---简单图片浏览器改变图像透明度

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

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content" >

        <Button
            android:id="@+id/button1"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="增大透明度" />

        <Button
            android:id="@+id/button2"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="减小透明度" />

        <Button
            android:id="@+id/button3"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="下一张" />
    </LinearLayout>
    <!-- 定义显示整体图片的ImageView -->

    <ImageView
        android:id="@+id/imageView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:background="#0000ff"
        android:scaleType="fitCenter"
        android:src="@drawable/shuangta" />
    <!-- 定义显示局部图片的ImageView -->

    <ImageView
        android:id="@+id/imageView2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="10dp"
        android:background="#0000ff" />

</LinearLayout>

package com.example.imageview;


import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.drawable.BitmapDrawable;
import android.os.Bundle;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.View.OnTouchListener;
import android.widget.Button;
import android.widget.ImageView;

public class MainActivity extends Activity {
    // 定义一个访问图片的数组
    int[] images = new int[] { R.drawable.lijiang, R.drawable.qiao,
            R.drawable.shuangta, R.drawable.shui, R.drawable.xiangbi,
            R.drawable.ic_launcher, };
    // 定义当前显示的图片
    int currentImage = 2;
    // 定义图片的初始透明度
    private int alpha = 255;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        final Button plusButton = (Button) findViewById(R.id.button1);
        final Button minuxButton = (Button) findViewById(R.id.button2);
        final Button nextButton = (Button) findViewById(R.id.button3);

        final ImageView imageview1 = (ImageView) findViewById(R.id.imageView1);
        final ImageView imageview2 = (ImageView) findViewById(R.id.imageView2);

        // 定义查看下一张图片的时间监听器
        nextButton.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View v) {
                if (currentImage >= 5) {
                    currentImage = -1;
                }
                BitmapDrawable bitmap = (BitmapDrawable) imageview1
                        .getDrawable();
                // 如果图片还没有回收，先强制回收图片
                if (!bitmap.getBitmap().isRecycled()) {
                    bitmap.getBitmap().recycle();
                }
                // 改变ImageView的图片
                imageview1.setImageBitmap(BitmapFactory.decodeResource(
                        getResources(), images[++currentImage]));
            }
        });

        // 定义改变图片透明度的方法
        OnClickListener listener = new OnClickListener() {

            @Override
            public void onClick(View v) {
                if (v == plusButton) {
                    alpha += 20;
                }
                if (v == minuxButton) {
                    alpha -= 20;
                }
                if (alpha > 255) {
                    alpha = 255;
                }
                if (alpha <= 0) {
                    alpha = 0;
                }
                // 改变图片的透明度
                imageview1.setAlpha(alpha);

            }
        };

        // 为2个按钮添加监听器
        plusButton.setOnClickListener(listener);
        minuxButton.setOnClickListener(listener);
        imageview1.setOnTouchListener(new OnTouchListener() {

            @Override
            public boolean onTouch(View arg0, MotionEvent arg1) {
                // TODO Auto-generated method stub
                BitmapDrawable bitmapDeaw = (BitmapDrawable) imageview1
                        .getDrawable();
                // 获取第一个图片显示框中的位图
                Bitmap bitmap = bitmapDeaw.getBitmap();
                double scale = bitmap.getWidth();
                // 或许需要显示图片的开始点
                int x = (int) (arg1.getX() * scale);
                int y = (int) (arg1.getY() * scale);
                if (x + 120 > bitmap.getWidth()) {
                    x = bitmap.getWidth() - 120;
                }
                if (y + 120 > bitmap.getHeight()) {
                    y = bitmap.getHeight() - 120;
                }

                // 显示图片的指定区域
                imageview2.setImageBitmap(Bitmap.createBitmap(bitmap, x, y,
                        120, 120));
                imageview2.setAlpha(alpha);
                return false;
            }
        });
    }

}