Android进阶篇-onTouchEvent的使用

这里通过演示一个可以拖动颜色球的例子来展示Android中onTouchEvent的使用以及自定义View。

实体类ColorBall：

/** * @author gongchaobin * * 实体类 颜色球 */public class ColorBall  { private Bitmap img; //小球的图片  private int coordX = 0; //画布上的X坐标 private int coordY = 0; //画布上的Y坐标 private int id;  private static int count = 1; private boolean goRight = true; private boolean goDown = true; public ColorBall(Context context, int drawable) {BitmapFactory.Options opts = new BitmapFactory.Options();        opts.inJustDecodeBounds = true;        img = BitmapFactory.decodeResource(context.getResources(), drawable);         id=count;count++;}public ColorBall(Context context, int drawable, Point point) {BitmapFactory.Options opts = new BitmapFactory.Options();        opts.inJustDecodeBounds = true;        img = BitmapFactory.decodeResource(context.getResources(), drawable);         id=count;count++;coordX= point.x;coordY = point.y;}public static int getCount() {return count;}void setX(int newValue) {        coordX = newValue;    }public int getX() {return coordX;}void setY(int newValue) {        coordY = newValue;   }public int getY() {return coordY;}public int getID() {return id;}public Bitmap getBitmap() {return img;}public void moveBall(int goX, int goY) {// check the borders, and set the direction if a border has reachedif (coordX > 270){goRight = false;}if (coordX < 0){goRight = true;}if (coordY > 400){goDown = false;}if (coordY < 0){goDown = true;}if (goRight){coordX += goX;}else{coordX -= goX;}if (goDown){coordY += goY;}else{coordY -= goY;}}}

自定义DrawView：

/** * @author gongchaobin *  * 自定义View */public class DrawView extends View {   private ColorBall[] colorballs = new ColorBall[3];    private int balID = 0;         public DrawView(Context context) {        super(context);        setFocusable(true);                 /**在画布上设置三个初始的点*/        Point point1 = new Point();        point1.x = 50;        point1.y = 20;        Point point2 = new Point();        point2.x = 100;        point2.y = 20;        Point point3 = new Point();        point3.x = 150;        point3.y = 20;                               /**New三个颜色球*/        colorballs[0] = new ColorBall(context,R.drawable.bol_groen, point1);        colorballs[1] = new ColorBall(context,R.drawable.bol_rood, point2);        colorballs[2] = new ColorBall(context,R.drawable.bol_blauw, point3);    }        @Override    protected void onDraw(Canvas canvas) {            /**重绘颜色球*/    for (ColorBall ball : colorballs) {            canvas.drawBitmap(ball.getBitmap(), ball.getX(), ball.getY(), null);        }    }        public boolean onTouchEvent(MotionEvent event) {        int eventaction = event.getAction();                 int X = (int)event.getX();         int Y = (int)event.getY();         switch (eventaction ) {         /**当初始进来的时候 ，向下移动的状态*/        case MotionEvent.ACTION_DOWN:         balID = 0;        for (ColorBall ball : colorballs) {        /**获取到小球的中心点*/        int centerX = ball.getX() + 25;        int centerY = ball.getY() + 25;                double radCircle  = Math.sqrt( (double) (((centerX-X)*(centerX-X)) + (centerY-Y)*(centerY-Y)));                /**如果移动的距离小于23，小球没动*/        if (radCircle < 23){        balID = ball.getID();                    break;        }              }             break;         /**balId>0,小球的移动状态*/        case MotionEvent.ACTION_MOVE:             if (balID > 0) {            colorballs[balID-1].setX(X-25);            colorballs[balID-1].setY(Y-25);            }            break;         case MotionEvent.ACTION_UP:              break;         }         /**invalidate方法 进行界面刷新重绘*/        invalidate();         return true;     }}