Android 在线问题

Question

我想在 LinearLayout 上添加一个 fling 动作。为此，我使用了以下代码。

public class NewsActivity extends Activity {

    ..........
    ...........
    private static final int SWIPE_MIN_DISTANCE = 120;
    private static final int SWIPE_MAX_OFF_PATH = 250;
    private static final int SWIPE_THRESHOLD_VELOCITY = 200;
    private GestureDetector gestureDetector;
    View.OnTouchListener gestureListener;



    @Override
    public void onCreate(Bundle savedInstanceState) {

       .....................
       .....................
       .....................

       LinearLayout newDeailsBlock = (LinearLayout) findViewById(R.id.newdeailsblock);
       // Gesture detection
       gestureDetector = new GestureDetector(new MyGestureDetector());
       gestureListener = new View.OnTouchListener() {

            @Override
            public boolean onTouch(View v, MotionEvent event) {
                // TODO Auto-generated method stub
                if (gestureDetector.onTouchEvent(event)) {
                    return true;
                }
                return false;
            }
        };
        newDeailsBlock.setOnTouchListener(gestureListener);
    }

    class MyGestureDetector extends SimpleOnGestureListener {
        @Override
        public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {
            try {
                Log.d("move","Swipe test");
                if (Math.abs(e1.getY() - e2.getY()) > SWIPE_MAX_OFF_PATH)
                    return false;
                // right to left swipe
                if(e1.getX() - e2.getX() > SWIPE_MIN_DISTANCE && Math.abs(velocityX) > SWIPE_THRESHOLD_VELOCITY) {                
                    Log.d("move","Left Swipe");
                }  else if (e2.getX() - e1.getX() > SWIPE_MIN_DISTANCE && Math.abs(velocityX) > SWIPE_THRESHOLD_VELOCITY) {
                    Toast.makeText(NewsActivity.this, "Right Swipe", Toast.LENGTH_SHORT).show();
                    Log.d("move","Right Swipe");
                }
            } catch (Exception e) {
                // nothing
            }
            return false;
        }

    }
}

但它根本不起作用 amd gestureDetector.onTouchEvent(event) 返回 false。我的代码有什么问题？

Answer 1

尝试让您的 Activity 扩展下面的抽象类，然后使用您想要的 fling 功能实现抽象方法 next() 和 previous() 。

public abstract class SwipeActivity extends Activity {
    private static final int SWIPE_MIN_DISTANCE = 120;
    private static final int SWIPE_MAX_OFF_PATH = 250;
    private static final int SWIPE_THRESHOLD_VELOCITY = 200;
    private GestureDetector gestureDetector;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        gestureDetector = new GestureDetector( new SwipeDetector() );
    }

    private class SwipeDetector extends SimpleOnGestureListener {       
        @Override
        public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX,
                float velocityY) {

            // Check movement along the Y-axis. If it exceeds SWIPE_MAX_OFF_PATH, then dismiss the swipe.
            if (Math.abs(e1.getY() - e2.getY()) > SWIPE_MAX_OFF_PATH)
                return false;

            // Swipe from right to left.
            // The swipe needs to exceed a certain distance (SWIPE_MIN_DISTANCE) and a certain velocity (SWIPE_THRESHOLD_VELOCITY).
            if (e1.getX() - e2.getX() > SWIPE_MIN_DISTANCE
                    && Math.abs(velocityX) > SWIPE_THRESHOLD_VELOCITY) {
                next();
                return true;
            }

            // Swipe from left to right.
            // The swipe needs to exceed a certain distance (SWIPE_MIN_DISTANCE) and a certain velocity (SWIPE_THRESHOLD_VELOCITY).
            if (e2.getX() - e1.getX() > SWIPE_MIN_DISTANCE
                    && Math.abs(velocityX) > SWIPE_THRESHOLD_VELOCITY) {
                previous();
                return true;
            }

            return false;
        }
    }

    @Override
    public boolean dispatchTouchEvent(MotionEvent ev) {
        //TouchEvent dispatcher.
        if (gestureDetector != null) {
            if (gestureDetector.onTouchEvent(ev))
                //If the gestureDetector handles the event, a swipe has been executed and no more needs to be done.
                return true;
        }
        return super.dispatchTouchEvent(ev);
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        return gestureDetector.onTouchEvent(event);
    }

    protected abstract void previous();
    protected abstract void next();
}