android 多点触摸实现图片缩放

package com.touch;
import android.graphics.Matrix;
import android.graphics.PointF;
import android.util.FloatMath;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnTouchListener;
import android.widget.ImageView;

public class MulitPointTouchListener implements OnTouchListener {
        Matrix matrix = new Matrix();
        Matrix savedMatrix = new Matrix();

        static final int NONE = 0;
        static final int DRAG = 1;
        static final int ZOOM = 2;
        int mode = NONE;

        PointF start = new PointF();
        PointF mid = new PointF();
        float oldDist = 1f;

        @Override
        public boolean onTouch(View v, MotionEvent event) {

                ImageView view = (ImageView) v;

                switch (event.getAction() & MotionEvent.ACTION_MASK) {
                case MotionEvent.ACTION_DOWN:

                        matrix.set(view.getImageMatrix());
                        savedMatrix.set(matrix);
                        start.set(event.getX(), event.getY());
                        mode = DRAG;

                      
                        break;
                case MotionEvent.ACTION_POINTER_DOWN:
                        oldDist = spacing(event);
                        if (oldDist > 10f) {
                                savedMatrix.set(matrix);
                                midPoint(mid, event);
                                mode = ZOOM;
                        }
                        break;
                case MotionEvent.ACTION_UP:
                case MotionEvent.ACTION_POINTER_UP:
                        mode = NONE;

                        break;
                case MotionEvent.ACTION_MOVE:
                        if (mode == DRAG) {
                                matrix.set(savedMatrix);
                                matrix.postTranslate(event.getX() - start.x, event.getY()
                                                - start.y);
                        } else if (mode == ZOOM) {
                                float newDist = spacing(event);
                                if (newDist > 10f) {
                                        matrix.set(savedMatrix);
                                        float scale = newDist / oldDist;
                                        matrix.postScale(scale, scale, mid.x, mid.y);
                                }
                        }
                        break;
                }

                view.setImageMatrix(matrix);
                return true;
        }

       
      
        private float spacing(MotionEvent event) {
                float x = event.getX(0) - event.getX(1);
                float y = event.getY(0) - event.getY(1);
                return FloatMath.sqrt(x * x + y * y);
        }

      
        private void midPoint(PointF point, MotionEvent event) {
                float x = event.getX(0) + event.getX(1);
                float y = event.getY(0) + event.getY(1);
                point.set(x / 2, y / 2);
        }
}

imageView.setOnTouchListener(new MulitPointTouchListener ());在xml中要将图片的缩放格式改成Matrix



注：android:scaleType="matrix"

注：此文档为转载

评论

2 楼 zhujinyuan 2012-08-29  

这种形式控制不了无限放大。

1 楼 烧伤的火柴 2011-12-02