Android实现的可以调整透明度的图片查看器实例

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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;
      }
    });
  }

}