JackTurky JackTurky - 28 days ago 13
Android Question

How to detect a swipe gesture on webview

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

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.

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