Android: How to handle right to left swipe gestures

Question

I want my app to recognize when a user swipes from right to left on the phone screen.

How to do this?

Answer 1

@Mirek Rusin answeir is very good. But, there is small bug, and fix is requried -

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) {
                            if (getOnSwipeListener() != null) {
                                getOnSwipeListener().onSwipeRight();
                            }
                        } else {
                            if (getOnSwipeListener() != null) {
                                getOnSwipeListener().onSwipeLeft();
                            }
                        }
                        result = true;
                    }
                }
                else if (Math.abs(diffY) > SWIPE_THRESHOLD && Math.abs(velocityY) > SWIPE_VELOCITY_THRESHOLD) {
                    if (diffY > 0) {
                        if (getOnSwipeListener() != null) {
                            getOnSwipeListener().onSwipeBottom();
                        }
                    } else {
                        if (getOnSwipeListener() != null) {
                            getOnSwipeListener().onSwipeTop();
                        }
                    }
                    result = true;
                }

What the difference? We set result = true, only if we have checked that all requrinments (both SWIPE_THRESHOLD and SWIPE_VELOCITY_THRESHOLD are Ok ). This is important if we discard swipe if some of requrinments are not achieved, and we have to do smth in onTouchEvent method of OnSwipeTouchListener!

Answer 2

If you want to display some buttons with actions when an list item is swipe are a lot of libraries on the internet that have this behavior. I implemented the library that I found on the internet and I am very satisfied. It is very simple to use and very quick. I improved the original library and I added a new click listener for item click. Also I added font awesome library (http://fortawesome.github.io/Font-Awesome/) and now you can simply add a new item title and specify the icon name from font awesome.

Here is the github link

Answer 3

To add an onClick as well, here's what I did.

....
// in OnSwipeTouchListener class

private final class GestureListener extends SimpleOnGestureListener {

    .... // normal GestureListener  code

   @Override
    public boolean onSingleTapConfirmed(MotionEvent e) {
        onClick(); // my method
        return super.onSingleTapConfirmed(e);
    }

} // end GestureListener class

    public void onSwipeRight() {
    }

    public void onSwipeLeft() {
    }

    public void onSwipeTop() {
    }

    public void onSwipeBottom() {
    }

    public void onClick(){ 
    }


    // as normal
    @Override
    public boolean onTouch(View v, MotionEvent event) {
        return gestureDetector.onTouchEvent(event);
}

} // end OnSwipeTouchListener class

---

I'm using Fragments, so using getActivity() for context. This is how I implemented it - and it works.

---

myLayout.setOnTouchListener(new OnSwipeTouchListener(getActivity()) {
            public void onSwipeTop() {
                Toast.makeText(getActivity(), "top", Toast.LENGTH_SHORT).show();
            }
            public void onSwipeRight() {
                Toast.makeText(getActivity(), "right", Toast.LENGTH_SHORT).show();
            }
            public void onSwipeLeft() {
                Toast.makeText(getActivity(), "left", Toast.LENGTH_SHORT).show();
            }
            public void onSwipeBottom() {
                Toast.makeText(getActivity(), "bottom", Toast.LENGTH_SHORT).show();
            }

            public void onClick(){
                Toast.makeText(getActivity(), "clicked", Toast.LENGTH_SHORT).show();
            }
        });

Answer 4

A little modification of @Mirek Rusin answer and now you can detect multitouch swipes. This code is on Kotlin:

class OnSwipeTouchListener(ctx: Context, val onGesture: (gestureCode: Int) -> Unit) : OnTouchListener {

private val SWIPE_THRESHOLD = 200
private val SWIPE_VELOCITY_THRESHOLD = 200

private val gestureDetector: GestureDetector

var fingersCount = 0

fun resetFingers() {
    fingersCount = 0
}

init {
    gestureDetector = GestureDetector(ctx, GestureListener())
}

override fun onTouch(v: View, event: MotionEvent): Boolean {
    if (event.pointerCount > fingersCount) {
        fingersCount = event.pointerCount
    }
    return gestureDetector.onTouchEvent(event)
}

private inner class GestureListener : SimpleOnGestureListener() {

    override fun onDown(e: MotionEvent): Boolean {
        return true
    }

    override fun onFling(e1: MotionEvent, e2: MotionEvent, velocityX: Float, velocityY: Float): Boolean {
        var result = false
        try {
            val diffY = e2.y - e1.y
            val diffX = e2.x - e1.x
            if (Math.abs(diffX) > Math.abs(diffY)) {
                if (Math.abs(diffX) > SWIPE_THRESHOLD && Math.abs(velocityX) > SWIPE_VELOCITY_THRESHOLD) {
                    if (diffX > 0) {
                        val gesture = when (fingersCount) {
                            1 -> Gesture.SWIPE_RIGHT
                            2 -> Gesture.TWO_FINGER_SWIPE_RIGHT
                            3 -> Gesture.THREE_FINGER_SWIPE_RIGHT
                            else -> -1
                        }
                        if (gesture > 0) {
                            onGesture.invoke(gesture)
                        }
                    } else {
                        val gesture = when (fingersCount) {
                            1 -> Gesture.SWIPE_LEFT
                            2 -> Gesture.TWO_FINGER_SWIPE_LEFT
                            3 -> Gesture.THREE_FINGER_SWIPE_LEFT
                            else -> -1
                        }
                        if (gesture > 0) {
                            onGesture.invoke(gesture)
                        }
                    }
                    resetFingers()
                }
            } else if (Math.abs(diffY) > SWIPE_THRESHOLD && Math.abs(velocityY) > SWIPE_VELOCITY_THRESHOLD) {
                if (diffY > 0) {
                    val gesture = when (fingersCount) {
                        1 ->  Gesture.SWIPE_DOWN
                        2 -> Gesture.TWO_FINGER_SWIPE_DOWN
                        3 -> Gesture.THREE_FINGER_SWIPE_DOWN
                        else -> -1
                    }
                    if (gesture > 0) {
                        onGesture.invoke(gesture)
                    }
                } else {
                    val gesture = when (fingersCount) {
                        1 ->  Gesture.SWIPE_UP
                        2 -> Gesture.TWO_FINGER_SWIPE_UP
                        3 -> Gesture.THREE_FINGER_SWIPE_UP
                        else -> -1
                    }
                    if (gesture > 0) {
                        onGesture.invoke(gesture)
                    }
                }
                resetFingers()
            }
            result = true

        } catch (exception: Exception) {
            exception.printStackTrace()
        }

        return result
    }
}}

Where Gesture.SWIPE_RIGHT and others are unique integer indentificator of gesture that I`m using to detect kind of gesture later in my activity:

rootView?.setOnTouchListener(OnSwipeTouchListener(this, {
    gesture -> log(Gesture.parseName(this, gesture))
}))

So you see gesture here is an integer variable that holds value I have passed before.

Answer 5

the usage of Edward Brey's answer in Kotlin

 view.setOnTouchListener(object: OnSwipeTouchListener(this) {
      override fun onSwipeLeft() {
        super.onSwipeLeft()
      }
      override fun onSwipeRight() {
        super.onSwipeRight()
      }
    }
 )

Answer 6

You don't need complicated calculations. It can be done just by using OnGestureListener interface from GestureDetector class.

Inside onFling method you can detect all four directions like this:

MyGestureListener.java:

import android.util.Log;
import android.view.GestureDetector;
import android.view.MotionEvent;

public class MyGestureListener implements GestureDetector.OnGestureListener{

    private static final long VELOCITY_THRESHOLD = 3000;

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

    @Override
    public void onShowPress(final MotionEvent e){ }

    @Override
    public boolean onSingleTapUp(final MotionEvent e){ return false; }

    @Override
    public boolean onScroll(final MotionEvent e1, final MotionEvent e2, final float distanceX,
                        final float distanceY){ return false; }

    @Override
    public void onLongPress(final MotionEvent e){ }

    @Override
    public boolean onFling(final MotionEvent e1, final MotionEvent e2,
                       final float velocityX,
                       final float velocityY){

        if(Math.abs(velocityX) < VELOCITY_THRESHOLD 
                    && Math.abs(velocityY) < VELOCITY_THRESHOLD){
            return false;//if the fling is not fast enough then it's just like drag
        }

        //if velocity in X direction is higher than velocity in Y direction,
        //then the fling is horizontal, else->vertical
        if(Math.abs(velocityX) > Math.abs(velocityY)){
            if(velocityX >= 0){
                Log.i("TAG", "swipe right");
            }else{//if velocityX is negative, then it's towards left
                Log.i("TAG", "swipe left");
            }
        }else{
            if(velocityY >= 0){
                Log.i("TAG", "swipe down");
            }else{
                Log.i("TAG", "swipe up");
            }
        }

        return true;
    }
}

usage:

GestureDetector mDetector = new GestureDetector(MainActivity.this, new MyGestureListener());

view.setOnTouchListener(new View.OnTouchListener(){
    @Override
    public boolean onTouch(final View v, final MotionEvent event){
        return mDetector.onTouchEvent(event);
    }
});