Android left/right swipe gesture in WebView activity (with clicking on links and vertical scrolling)

Question

SOLVED, solution is underneath.

I want to replace buttons for navigation in webview to 2 swipe gestures - left and right swipe. This Android: How to handle right to left swipe gestures link really helped me, but I encountered problem - after implementing this code I was unable to click on links/ or scroll through loaded webpage in webview activity(I have used 1st answer from possible answers).

Then I found out that in another answer in this question is something similar - how to scroll in listview - https://mcmap.net/q/74031/-android-how-to-handle-right-to-left-swipe-gestures, but I wasn't able to get it running. In logcat i get this debug info: http://s27.postimg.org/5qfipgi1v/message.png

This is my OnSwipeTouchListener:

import android.view.GestureDetector;
import android.view.GestureDetector.SimpleOnGestureListener;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnTouchListener;

public class OnSwipeTouchListener implements OnTouchListener {

private final GestureDetector gestureDetector = new GestureDetector(new GestureListener());

public boolean onTouch(final View view, final MotionEvent motionEvent) {
    return gestureDetector.onTouchEvent(motionEvent);
}

private final class GestureListener extends SimpleOnGestureListener {

    private static final int SWIPE_THRESHOLD = 100;
    private static final int SWIPE_VELOCITY_THRESHOLD = 100;

    @Override
    public boolean onDown(MotionEvent e) {
        return true;
    }

    @Override
    public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {
        boolean result = false;
        try {
            float diffY = e2.getY() - e1.getY();
            float diffX = e2.getX() - e1.getX();
            if (Math.abs(diffX) > Math.abs(diffY)) {
                if (Math.abs(diffX) > SWIPE_THRESHOLD && Math.abs(velocityX) > SWIPE_VELOCITY_THRESHOLD) {
                    if (diffX > 0) {
                        onSwipeRight();
                    } else {
                        onSwipeLeft();
                    }
                }
            }
        } catch (Exception exception) {
            exception.printStackTrace();
        }
        return result;
    }
}

public void onSwipeRight() {
}

public void onSwipeLeft() {
}

public GestureDetector getGestureDetector(){
    return  gestureDetector;
}
}

And my webview activity(stripped):

public class WebViewActivity extends Activity {
private WebView browser;
    private OnSwipeTouchListener onSwipeTouchListener;
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.webview);
            onSwipeTouchListener = new OnSwipeTouchListener() {
public void onSwipeRight() {
    Toast.makeText(WebViewActivity.this, "right", Toast.LENGTH_SHORT).show();
}
public void onSwipeLeft() {
    Toast.makeText(WebViewActivity.this, "left", Toast.LENGTH_SHORT).show();
}
};

browser.setOnTouchListener(onSwipeTouchListener);
} // end of onCreate
@Override
public boolean dispatchTouchEvent(MotionEvent ev){
    onSwipeTouchListener.getGestureDetector().onTouchEvent(ev); 
        return super.dispatchTouchEvent(ev);   
}
} // end of WebViewActivity

How to make left/right swiping, vertical scrolling and clicking on links working at the same time?

SOLUTION: Same solved question: Fling Gesture and Webview in Android

Mithras

Answer 1

I'm not familiar enough with the GestureDetector to reliably diagnose your problem. One thing you could try is cloning the event:

@Override
public boolean dispatchTouchEvent(MotionEvent ev){
    onSwipeTouchListener.getGestureDetector().onTouchEvent(MotionEvent.obtain(ev)); 
    return super.dispatchTouchEvent(ev);   
}

Failing that another way to approach this is to use onOverScrolled instead of a GestureDetector:

@Override
protected void onOverScrolled (int scrollX, int scrollY, boolean clampedX, boolean clampedY) {
    if (scrollX > (getWidth() + THRESHOLD) && clampedX) {
        onSwipeLeft();
    }
    if (scrollX < - THRESHOLD && clampedX) {
        onSwipeRight();
    }
    super.onOverScrolled(scrollX, scrollY, clampedX, clampedY);
}

This does assume that your content is not normally scrollable sideways though.

Intended

Adding MotionEvent.obtain(ev) doesn't change anything, there is still no vertical scrolling and debug output is same as previous. Overriding onOverScrolled doesn't work, because this expect scrollable sideways. If I don't scroll to the side, then scrollX is still zero and onSwipeLeft/Right won't occur. – Mithras