Android实现的可以调整透明度的图片查看器实例

<?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 android.demo;

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 androiddemo5activity 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.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;
      }
    });
  }

}