android小項目—自由拖拽縮放圖片

布局檔案

<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    android:layout_width="fill_parent"    android:layout_height="fill_parent" >    <ImageView        android:id="@+id/image_view"        android:layout_width="fill_parent"        android:layout_height="fill_parent"        android:scaleType="matrix"        android:src="@drawable/test" >    </ImageView></LinearLayout>

java代碼如下

package mutl.touch.sample;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;public class Main extends Activity {private static final int NONE = 0;private static final int DRAG = 1;private static final int ZOOM = 2;private int mode = NONE;private float oldDist;private Matrix matrix = new Matrix();private Matrix savedMatrix = new Matrix();private PointF start = new PointF();private PointF mid = new PointF();public void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.main);ImageView view = (ImageView) findViewById(R.id.image_view);view.setOnTouchListener(new OnTouchListener() {public boolean onTouch(View v, MotionEvent event) {ImageView view = (ImageView) v;switch (event.getAction() & MotionEvent.ACTION_MASK) {case MotionEvent.ACTION_DOWN:savedMatrix.set(matrix);start.set(event.getX(), event.getY());System.out.println("ACTION_DOWN = (" + event.getX() + ","+ event.getY() + ")");mode = DRAG;break;case MotionEvent.ACTION_UP:case MotionEvent.ACTION_POINTER_UP:System.out.println("ACTION_POINTER_UP = (" + event.getX()+ "," + event.getY() + ")");mode = NONE;break;case MotionEvent.ACTION_POINTER_DOWN:oldDist = spacing(event);if (oldDist > 10f) {savedMatrix.set(matrix);midPoint(mid, event);mode = ZOOM;}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);}});}}