android图片的拖拉以及放大缩小控制
直接上代码，代码很清楚。
import android.app.Activity;import android.graphics.Bitmap;import android.graphics.BitmapFactory;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.view.ViewGroup.MarginLayoutParams;import android.widget.ImageView;public class MainActivity extends Activity implements OnTouchListener {/** Called when the activity is first created. */// 放大缩小Matrix matrix = new Matrix();Matrix savedMatrix = new Matrix();PointF start = new PointF();PointF mid = new PointF();float oldDist;private ImageView myImageView;// 模式static final int NONE = 0;static final int DRAG = 1;static final int ZOOM = 2;int mode = NONE;@Overridepublic void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);myImageView = (ImageView) findViewById(R.id.myImage);myImageView.setOnTouchListener(this);}@Overridepublic boolean onTouch(View v, MotionEvent event) {ImageView myImageView = (ImageView) v;switch (event.getAction() & MotionEvent.ACTION_MASK) {// 设置拖拉模式case MotionEvent.ACTION_DOWN:matrix.set(myImageView.getImageMatrix());savedMatrix.set(matrix);start.set(event.getX(), event.getY());mode = DRAG;break;case MotionEvent.ACTION_UP:case MotionEvent.ACTION_POINTER_UP:mode = NONE;break;// 设置多点触摸模式case MotionEvent.ACTION_POINTER_DOWN:oldDist = spacing(event);if (oldDist > 10f) {savedMatrix.set(matrix);midPoint(mid, event);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);matrix.postTranslate(event.getX() - start.x, event.getY()- start.y);}// 若为ZOOM模式，则点击触摸缩放else if (mode == ZOOM) {float newDist = spacing(event);if (newDist > 10f) {matrix.set(savedMatrix);float scale = newDist / oldDist;// 设置硕放比例和图片的中点位置matrix.postScale(scale, scale, mid.x, mid.y);}}break;}myImageView.setImageMatrix(matrix);return true;}// 计算移动距离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);}// 计算中点位置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);}}