学习android第一篇：图片的放大缩小

package okay.incorruptrelics.bll;import android.graphics.Matrix;import android.graphics.PointF;import android.util.FloatMath;import android.util.Log;import android.view.MotionEvent;import android.view.View;import android.view.View.OnTouchListener;import android.widget.ImageView;public class ImageMatrix implements OnTouchListener {private static final String TAG = "Touch";public static ImageView view;Matrix matrix = new Matrix();Matrix savedMatrix = new Matrix();PointF start = new PointF();PointF first = new PointF();PointF mid = new PointF();float oldDist;// 设备高 宽int dwidth, dheight;// 图片高宽int widOrg, heightOrg;// We can be in one of these 3 statesstatic final int NONE = 0;static final int DRAG = 1;static final int ZOOM = 2;int mode = NONE;@Overridepublic boolean onTouch(View v, MotionEvent event) {// TODO Auto-generated method stubview = (ImageView) v;widOrg = view.getWidth();heightOrg = view.getHeight();switch (event.getAction() & MotionEvent.ACTION_MASK) {// 设置拖拉模式case MotionEvent.ACTION_DOWN:savedMatrix.set(matrix);start.set(event.getX(), event.getY());first.set(event.getX(), event.getY());// Log.d(TAG, "mode=DRAG");mode = DRAG;break;case MotionEvent.ACTION_UP:float x = event.getX(0) - first.x;float y = event.getY(0) - first.y;break;case MotionEvent.ACTION_POINTER_UP:mode = NONE;// Log.d(TAG, "mode=NONE");break;// 设置多点触摸模式case MotionEvent.ACTION_POINTER_DOWN:oldDist = spacing(event);Log.d(TAG, "oldDist=" + oldDist);if (oldDist > 10f) {savedMatrix.set(matrix);midPoint(mid, event);mode = ZOOM;// Log.d(TAG, "mode=ZOOM");}break;// 若为DRAG模式，则点击移动图片case MotionEvent.ACTION_MOVE:if (mode == DRAG) {matrix.set(savedMatrix);// 设置位移matrix.postTranslate(event.getX() - start.x, event.getY()- start.y);// start.set(event.getX(), event.getY());}// 若为ZOOM模式，则多点触摸缩放else if (mode == ZOOM) {float newDist = spacing(event);// Log.d(TAG, "newDist=" + newDist);if (newDist > 10f) {matrix.set(savedMatrix);float scale = newDist / oldDist;// 设置缩放比例和图片中点位置matrix.postScale(scale, scale, mid.x, mid.y);}// oldDist=newDist;}break;}view.setImageMatrix(matrix);return true;}/** * 计算拖动的距离 *  * @param event * @return */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);}/** * 计算两点的之间的中间点 *  * @param point * @param event */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);}}