Bitmap旋转和缩放

MainActivity如下:

package cn.testtouchscreentomoveimage;
import android.app.Activity;
import android.graphics.Matrix;
import android.graphics.PointF;
import android.os.Bundle;
import android.util.FloatMath;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnTouchListener;
import android.widget.ImageView;
/**
 * Demo描述:
 * 实现图片的拖动和缩放
 * 
 * 参考资料:
 * 1 http://blog.csdn.net/lfdfhl/article/details/8248848
 * 2 http://blog.csdn.net/leverage_1229/article/details/9009931
 * 
 * 注意事项:
 * 在该Demo中对于ImageView的设置
 * android:layout_width="match_parent"
 * android:layout_height="match_parent"
 * 是不太合理的,在具体项目中应调整
 */

public class MainActivity extends Activity {
    private ImageView mImageView;
    // 开始点
    private PointF mStartPoinF ;
    // 图片位置的变换矩阵
    private Matrix mMatrix;
    // 图片当前矩阵
    private Matrix mCurrentMatrix;
    // 模式参数
    private int current_mode = 0;
    // 拖拉模式
    private static final int drag_mode = 1;
    // 缩放模式
    private static final int zoom_mode = 2;
    // 开启缩放的阈值
    private static final float ZOOM_THRESHOLD = 10.0f;
    // 缩放前两指间的距离
    private float before_move_twoFingers_distance;
    // 两指移动后两者间的距离
    private float after_move_twoFingers_distance;
    // 两指间中心点
    private PointF mMiddlePointF;
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        init();
    }

	private void init() {
		mStartPoinF = new PointF();
		mMatrix = new Matrix();
		mCurrentMatrix = new Matrix();
		mImageView = (ImageView) findViewById(R.id.imageView);
		mImageView.setOnTouchListener(new TouchListenerImpl());
	}

	private class TouchListenerImpl implements OnTouchListener {
		@Override
		public boolean onTouch(View v, MotionEvent event) {
			switch (event.getAction() & MotionEvent.ACTION_MASK) {
			case MotionEvent.ACTION_DOWN:
				current_mode = drag_mode;
				// 记录图片当前matrix
				mCurrentMatrix.set(mImageView.getImageMatrix());
				// 记录开始坐标
				mStartPoinF.set(event.getX(), event.getY());
				break;

			// 当屏幕上已经有触点(手指),再有手指按下时触发该事件
			case MotionEvent.ACTION_POINTER_DOWN:
				current_mode = zoom_mode;
				before_move_twoFingers_distance = getTwoPointsDistance(event);
				if (before_move_twoFingers_distance > ZOOM_THRESHOLD) {
					// 计算两触点的中心点
					mMiddlePointF = getMiddlePoint(event);
					// 记录图片当前matrix
					mCurrentMatrix.set(mImageView.getImageMatrix());
				}
				break;

			case MotionEvent.ACTION_MOVE:
				//处理图片的拖动
				if (current_mode == drag_mode) {
					// 获取X轴移动距离
					float distanceX = event.getX() - mStartPoinF.x;
					// 获取Y轴移动距离
					float distanceY = event.getY() - mStartPoinF.y;
					// 在mCurrentMatrix的基础上平移图片
					mMatrix.set(mCurrentMatrix);
					mMatrix.postTranslate(distanceX, distanceY);
					
				} 
				//处理图片的缩放
				if (current_mode == zoom_mode) {
					after_move_twoFingers_distance = getTwoPointsDistance(event);
					if (after_move_twoFingers_distance > ZOOM_THRESHOLD) {
						// 计算缩放比例
						float scale = after_move_twoFingers_distance / before_move_twoFingers_distance;
						mMatrix.set(mCurrentMatrix);
						// 依据缩放比例和中心点进行缩放
						mMatrix.postScale(scale, scale, mMiddlePointF.x,mMiddlePointF.y);
					}
				}
				break;

			case MotionEvent.ACTION_UP:
			// 当手指离开屏幕,但屏幕上仍有其他触点(手指)时触发该事件
			case MotionEvent.ACTION_POINTER_UP:
				current_mode = 0;
				break;
			}
			// 为ImageView设置matrix
			mImageView.setImageMatrix(mMatrix);
			return true;
		}

	}
    
     //计算两点之间的距离
    public static float getTwoPointsDistance(MotionEvent event) {
        float disX = event.getX(1) - event.getX(0);
        float disY = event.getY(1) - event.getY(0);
        return FloatMath.sqrt(disX * disX + disY * disY);
    }
   
     //计算两点之间的中间点
    public static PointF getMiddlePoint(MotionEvent event) {
        float midX = (event.getX(0) + event.getX(1)) /2;
        float midY = (event.getY(0) + event.getY(1)) /2;
        return new PointF(midX, midY);
    }
}

main.xml如下:

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

    <ImageView
       android:id="@+id/imageView"
       android:layout_width="match_parent"
       android:layout_height="match_parent"
       android:src="@drawable/e"
       android:scaleType="matrix" 
    />

</LinearLayout>