How to detect a swipe gesture on webview

Question

i'm developing a simple android application with a RelativeLayout and a WebView inside.

I have to detect swipe from bottom to top done only in the 20% of the left part of the screen. So when user swipe in that space from bottom to top i have to show a custom dialog.

What i try is:

import android.app.Activity;
import android.view.MotionEvent;
import android.view.View;

public class ActivitySwipeDetector implements View.OnTouchListener {

    static final String logTag = "ActivitySwipeDetector";
    private Activity activity;
    static final int MIN_DISTANCE = 100;
    private float downY, upY;

    public ActivitySwipeDetector(Activity activity){
        this.activity = activity;
    }

    public void onRightToLeftSwipe(){

    }

    public void onLeftToRightSwipe(){

    }

    public void onTopToBottomSwipe(){

    }

    public void onBottomToTopSwipe(){
        System.out.println("BOTTOM TO TOP SWIPE DONE!");
    }

    public boolean onTouch(View v, MotionEvent event) {
        switch(event.getAction()){
        case MotionEvent.ACTION_DOWN: {
            downY = event.getY();
            return true;
        }
        case MotionEvent.ACTION_UP: {
            upY = event.getY();
            float deltaY = downY - upY;
            if(Math.abs(deltaY) > MIN_DISTANCE){
                if(deltaY > 0) { this.onBottomToTopSwipe(); return true; }
            }
            else {
                return false;
            }

            return true;
        }
        }
        return false;
    }

}

    layout = (RelativeLayout)this.findViewById(R.id.layout);
    layout.setOnTouchListener(activitySwipeDetector);

But it doesn't do nothing!

So i try creating a custom webview in this way:

import android.content.Context;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.webkit.WebView;

public class MyWebView extends WebView {
    public MyWebView(Context context) {
        super(context);
    }
    public MyWebView(Context context,AttributeSet set){
        super(context,set);
    }



    @Override 
    public boolean onTouchEvent(MotionEvent evt) {   

        boolean consumed = super.onTouchEvent(evt); 
        if (isClickable()) { 
            switch (evt.getAction()) { 
            case MotionEvent.ACTION_DOWN:  
                lastTouchY = evt.getY();
                downTime = evt.getEventTime();
                hasMoved = false; 
                break; 
            case MotionEvent.ACTION_MOVE: 
                hasMoved = moved(evt); 
                break; 
            case MotionEvent.ACTION_UP: 
                float actualTouchY = evt.getY();
                long currentTime = evt.getEventTime();
                float difference = Math.abs(lastTouchY - actualTouchY);
                long time = currentTime - downTime;

                if ( (lastTouchY < actualTouchY) && (time < 220) && (difference > 100) ) {
                    System.out.println("SWIPE1");
                }
                if ( (lastTouchY > actualTouchY) && (time < 220) && (difference > 100) ) {
                    System.out.println("SWIPE2");
                }
                break; 
            } 
        } 
        return consumed || isClickable(); 
    } 
    long downTime;
    private float lastTouchY; 
    private boolean hasMoved = false; 
    private boolean moved(MotionEvent evt) { 
        return hasMoved || 
                Math.abs(evt.getY() - lastTouchY) > 10.0; 
    }

}

but with no success!!! can someone help me?? THAnks!!!!! :)

Answer 1

Use a GestureDetector with a custom web view..

webView.setGestureDetector(new GestureDetector(new CustomeGestureDetector()));   

the gesture detector:

private class CustomeGestureDetector extends SimpleOnGestureListener {      
    @Override
    public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {
        if(e1 == null || e2 == null) return false;
        if(e1.getPointerCount() > 1 || e2.getPointerCount() > 1) return false;
        else {
            try { // right to left swipe .. go to next page
                if(e1.getX() - e2.getX() > 100 && Math.abs(velocityX) > 800) {
                    //do your stuff
                    return true;
                } //left to right swipe .. go to prev page
                else if (e2.getX() - e1.getX() > 100 && Math.abs(velocityX) > 800) {
                    //do your stuff
                    return true;
                } //bottom to top, go to next document
                else if(e1.getY() - e2.getY() > 100 && Math.abs(velocityY) > 800 
                        && webView.getScrollY() >= webView.getScale() * (webView.getContentHeight() - webView.getHeight())) {
                    //do your stuff
                    return true;
                } //top to bottom, go to prev document
                else if (e2.getY() - e1.getY() > 100 && Math.abs(velocityY) > 800 ) {
                    //do your stuff
                    return true;
                } 
            } catch (Exception e) { // nothing
            }
            return false;
        }
    }
}

The custom web view:

public final class CustomWebView extends WebView {

private GestureDetector gestureDetector;

/**
 * @param context
 * @param attrs
 * @param defStyle
 */
public CustomWebView(Context context) {
    super(context);
}

/**
 * @param context
 * @param attrs
 * @param defStyle
 */
public CustomWebView(Context context, AttributeSet attrs) {
    super(context, attrs);
}

/**
 * @param context
 * @param attrs
 * @param defStyle
 */
public CustomWebView(Context context, AttributeSet attrs, int defStyle) {
    super(context, attrs, defStyle);
}

/* 
 * @see android.webkit.WebView#onScrollChanged(int, int, int, int)
 */
@Override
protected void onScrollChanged(int l, int t, int oldl, int oldt) {
    super.onScrollChanged(l, t, oldl, oldt);
}

/* 
 * @see android.webkit.WebView#onTouchEvent(android.view.MotionEvent)
 */
@Override
public boolean onTouchEvent(MotionEvent ev) {
    return gestureDetector.onTouchEvent(ev) || super.onTouchEvent(ev);
}

public void setGestureDetector(GestureDetector gestureDetector) {
    this.gestureDetector = gestureDetector;
}
}

As said by Андрей Москвичёв:

It can be solved without deriving WebView class, by registering touch listener: webview.setOnTouchListener(new OnTouchListener() ...) and calling gestureDetector.onTouchEvent(ev) from it.

Answer 2

The 'webView.setGestureDetector(new GestureDetector(' solution is deprecated.

The next solution is simple to implement. Scrolling, clicking on links still works.

1 - Add this to your webView:

webView.setOnTouchListener( new OnSwipeWebviewTouchListener( getActivity(), this));

The 'this' means that you have your calling class implement the TouchListener interface methods. You can implement YOUR navigation via the methods onSwipeRight() and onSwipeLeft().

2 - Use this OnTouchListener:

public class OnSwipeWebviewTouchListener implements View.OnTouchListener {
    private final GestureDetector gestureDetector;
    public OnSwipeWebviewTouchListener(Context ctx, TouchListener touchListener) {
        gestureDetector = new GestureDetector(ctx, new GestureListener(touchListener));
    }
    @Override
    public boolean onTouch(View v, MotionEvent event) {
        return gestureDetector.onTouchEvent(event);
    }
    private final class GestureListener extends GestureDetector.SimpleOnGestureListener {
        private TouchListener touchListener;
        GestureListener(TouchListener touchListener) {
            super();
            this.touchListener = touchListener;
        }
        @Override
        public boolean onDown(MotionEvent e) {
            return false;  // THIS does the trick
        }
        @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)) {
                    // You can customize these settings, so 30 is an example
                    if (Math.abs(diffX) > 30 && Math.abs(velocityX) > 30) {
                        if (diffX > 0) {
                            touchListener.onSwipeRight();
                        } else {
                            touchListener.onSwipeLeft();
                        }
                        result = true;
                    }
                } else {
                    result = false;
                }
            } catch (Exception exception) {
                exception.printStackTrace();
            }
            return result;
        }
    }
}

3 - An example of the TouchListner could be:

public interface TouchListener  {
    default void onSwipeLeft() {
        Logger.d( "Swipe left");
    }
    default void onSwipeRight() {
        Logger.d( "Swipe right");
    }
}