Android的数据存储与IO - 手势

Android的数据存储与IO - 手势

关于手势的知识，我是第一次接触，是Android提供的另类的IO

可以进行手势检测、通过指定手势完成相应的动作、可以自行添加手势到手势库，也可以识别手势

下面是一个实例：通过手势缩放图片

创建项目：GestureZoom

运行项目效果如下：

Activity文件：GestureZoom

package wwj.gesturezoom;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 GestureZoom extends Activity implements OnGestureListener {//定义手势检测器实例GestureDetector detector;ImageView imageView;//初始图片资源Bitmap bitmap;//定义图片的宽、高int width, height;//记录当前的缩放比float currentScale = 1;//控制图片缩放的Matrix对象Matrix matrix;    @Override    public void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.main);        //创建手势检测器        detector = new GestureDetector(this);        imageView = (ImageView)findViewById(R.id.show);        matrix = new Matrix();        //获取被缩放的源图片        bitmap = BitmapFactory.decodeResource(this.getResources(), R.drawable.flower);        //获得位图宽        width = bitmap.getWidth();        //获得位图高        height = bitmap.getHeight();        //设置ImageView初始化时显示的图片        imageView.setImageBitmap(BitmapFactory.decodeResource(this.getResources(), R.drawable.flower));    }    @Override    public boolean onTouchEvent(MotionEvent event) {    // TODO Auto-generated method stub    //将该Acitivity上触碰事件交给GestureDetector处理    return 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;velocityY = velocityY < -4000 ? -4000 : velocityY;//根据手势的速度来计算缩放比，如果velocity > 0, 放大图像，否则缩小图像currentScale += currentScale * velocityX / 4000.0f;//保证currentScale不会等于0currentScale = currentScale > 0.01 ? currentScale : 0.01f;//重置Matrixmatrix.reset();//缩放Matrixmatrix.setScale(currentScale, currentScale, 160, 200);BitmapDrawable tmp = (BitmapDrawable) imageView.getDrawable();//如果图片还未回收，先强制回收该图片if(!tmp.getBitmap().isRecycled()){tmp.getBitmap().recycle();}//根据原始位图和Matrix创建新图片Bitmap bitmap2 = Bitmap.createBitmap(bitmap, 0, 0, width, height, matrix, true);//显示新的位图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;}    }