Android的数据存储与IO - 手势
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 stub
- return false;
- }
- public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX,
- float velocityY) {
- // TODO Auto-generated method stub
- velocityX = 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0
- currentScale = currentScale > 0.01 ? currentScale : 0.01f;
- //重置Matrix
- matrix.reset();
- //缩放Matrix
- matrix.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 stub
- return false;
- }
- public void onShowPress(MotionEvent e) {
- // TODO Auto-generated method stub
- }
- public boolean onSingleTapUp(MotionEvent e) {
- // TODO Auto-generated method stub
- return false;
- }
- }
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