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;      }    });  }}