Android编程实现图片放大缩小功能ZoomControls控件用法实例

package example.com.myapplication;
import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Matrix;
import android.os.Bundle;
import android.util.DisplayMetrics;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.ImageView;
import android.widget.LinearLayout;
import android.widget.ZoomControls;
public class MainActivity extends Activity {
  private LinearLayout llLayout;
  private ZoomControls zoomcontrols;
  private ImageView img;
  private int id=0;
  private int displayWidth;
  private int displayHeight;
  private float scaleWidth = 1;
  private float scaleHeight = 1;
  private Bitmap bitmap;
  @Override
  public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    llLayout =(LinearLayout)findViewById(R.id.layout);
    //取得屏幕分辨率大小
    DisplayMetrics dm = new DisplayMetrics();
    getWindowManager().getDefaultDisplay().getMetrics(dm);
    displayWidth = dm.widthPixels;
    //屏幕高度减去zoomControls的高度
    displayHeight = dm.heightPixels;
    bitmap = BitmapFactory.decodeResource(getResources(), R.drawable.c);
    img =(ImageView)findViewById(R.id.image);
    //zoom.hide();隐藏zoomControls
    //zoom.show();显示zoomCOntrols
    zoomcontrols =(ZoomControls)findViewById(R.id.zoomcontrol);
    img =(ImageView)findViewById(R.id.image);
    zoomcontrols.setIsZoomInEnabled(true);
    zoomcontrols.setIsZoomOutEnabled(true);
    //图片放大
    zoomcontrols.setOnZoomInClickListener(new OnClickListener()
    {
      public void onClick(View v)
      {
        int bmpWidth = bitmap.getWidth();
        int bmpHeight = bitmap.getHeight();
        //设置图片放大但比例
        double scale = 1.25;
        //计算这次要放大的比例
        scaleWidth =(float)(scaleWidth*scale);
        scaleHeight =(float)(scaleHeight*scale);
        //产生新的大小但Bitmap对象
        Matrix matrix = new Matrix();
        matrix.postScale(scaleWidth, scaleHeight);
        Bitmap resizeBmp = Bitmap.createBitmap(bitmap,0,0,bmpWidth,bmpHeight,matrix,true);
        img.setImageBitmap(resizeBmp);
      }
    });
    //图片减小
    zoomcontrols.setOnZoomOutClickListener(new OnClickListener()
    {
      public void onClick(View v) {
        int bmpWidth = bitmap.getWidth();
        int bmpHeight = bitmap.getHeight();
        //设置图片放大但比例
        double scale = 0.8;
        //计算这次要放大的比例
        scaleWidth =(float)(scaleWidth*scale);
        scaleHeight =(float)(scaleHeight*scale);
        //产生新的大小但Bitmap对象
        Matrix matrix = new Matrix();
        matrix.postScale(scaleWidth, scaleHeight);
        Bitmap resizeBmp = Bitmap.createBitmap(bitmap,0,0,bmpWidth,bmpHeight,matrix,true);
        img.setImageBitmap(resizeBmp);
      }
    });
  }
}

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
  android:orientation="vertical"
  android:layout_width="fill_parent"
  android:layout_height="fill_parent"
  android:id="@+id/layout"
  >
  <ImageView
    android:id="@+id/image"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:src="@drawable/c"
    />
  <ZoomControls
    android:id="@+id/zoomcontrol"
    android:layout_gravity="bottom"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    />
  </LinearLayout>