android小項目—通過手勢縮放圖片

本執行個體是通過《瘋狂android講義》上的範例：親自打出來貼一下，從左往右手勢是放大，從右往左是縮小

package com.example.demogesture;import android.app.Activity;import android.graphics.Bitmap;import android.graphics.BitmapFactory;import android.graphics.Matrix;import android.graphics.drawable.BitmapDrawable;import android.os.Bundle;import android.view.GestureDetector;import android.view.GestureDetector.OnGestureListener;import android.view.MotionEvent;import android.widget.ImageView;public class MainActivity extends Activity implements OnGestureListener {// 定義手勢檢測器GestureDetector detector;ImageView imageView;Bitmap bitmap;// 初始的圖片資源int width, height;float currentScale = 1;// 圖片的縮放比Matrix matrix;// 控製圖片縮放的矩陣對象@Overridepublic void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);super.setContentView(R.layout.activity_main);imageView = (ImageView) findViewById(R.id.imageView1);detector = new GestureDetector(this);matrix = new Matrix();bitmap = BitmapFactory.decodeResource(getResources(), R.drawable.aaa);width = bitmap.getWidth();height = bitmap.getHeight();// 設定imageView初始化時的圖片,必須這樣，如果改為bitmap後會報錯imageView.setImageBitmap(BitmapFactory.decodeResource(getResources(),R.drawable.aaa));}@Overridepublic boolean onTouchEvent(MotionEvent event) {// TODO Auto-generated method stubreturn detector.onTouchEvent(event);}public boolean onDown(MotionEvent e) {// TODO Auto-generated method stubreturn false;}public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX,float velocityY) {// TODO Auto-generated method stubvelocityX = velocityX > 4000 ? 4000 : velocityX;velocityX = velocityX < -4000 ? -4000 : velocityX;// 根據手勢的速度來計算縮放比，如果velocityX>0,放大映像，否則縮小映像currentScale += currentScale * velocityX / 4000.0f;// 保證currentScale不會為0currentScale = currentScale > 0.01f ? currentScale : 0.01f;// 重設Matrixmatrix.reset();matrix.setScale(currentScale, currentScale, 160, 200);BitmapDrawable tmp = (BitmapDrawable) imageView.getDrawable();// 如果圖片還未回收，先強制回收圖片if (!tmp.getBitmap().isRecycled()) {tmp.getBitmap().recycle();}// 根據原始位置和Matrix建立新圖片Bitmap bitmap2 = Bitmap.createBitmap(bitmap, 0, 0, width, height,matrix, true);imageView.setImageBitmap(bitmap2);return true;}public void onLongPress(MotionEvent e) {// TODO Auto-generated method stub}public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX,float distanceY) {// TODO Auto-generated method stubreturn false;}public void onShowPress(MotionEvent e) {// TODO Auto-generated method stub}public boolean onSingleTapUp(MotionEvent e) {// TODO Auto-generated method stubreturn false;}}