[android] How to detect the swipe left or Right in Android?

the best answer is @Gal Rom 's. there is more information about it: touch event return's to child views first. and if you define onClick or onTouch listener for them, parnt view (for example fragment) will not receive any touch listener. So if you want define swipe listener for fragment in this situation, you must implement it in a new class:

    package com.neganet.QRelations.fragments;

import android.content.Context;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.widget.FrameLayout;

public class SwipeListenerFragment extends FrameLayout {
    private float x1,x2;
    static final int MIN_DISTANCE=150;
    private onSwipeEventDetected mSwipeDetectedListener;


    public SwipeListenerFragment(Context context) {
        super(context);
    }

    public SwipeListenerFragment(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    public SwipeListenerFragment(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
    }

    @Override
    public boolean onInterceptTouchEvent(MotionEvent ev) {
        boolean result=false;
        switch(ev.getAction())
        {
            case MotionEvent.ACTION_DOWN:
                x1 = ev.getX();
                break;
            case MotionEvent.ACTION_UP:
                x2 = ev.getX();
                float deltaX = x2 - x1;
                if (Math.abs(deltaX) > MIN_DISTANCE)
                {
                    if(deltaX<0)
                    {
                        result=true;
                        if(mSwipeDetectedListener!=null)
                            mSwipeDetectedListener.swipeLeftDetected();

                    }else if(deltaX>0){
                        result=true;
                        if(mSwipeDetectedListener!=null)
                            mSwipeDetectedListener.swipeRightDetected();
                    }
                }
                break;
        }
        return result;
    }

    public interface onSwipeEventDetected
    {
        public void swipeLeftDetected();
        public void swipeRightDetected();

    }

    public void registerToSwipeEvents(onSwipeEventDetected listener)
    {
        this.mSwipeDetectedListener=listener;
    }
}

I changed @Gal Rom 's class. So it can detect both right and left swipe and specially it returns onInterceptTouchEvent true after detect. its important because if we dont do it some times child views maybe receive event and both of Swipe for fragment and onClick for child view (for example) runs and cause some issues. after making this class, you must change your fragment xml file:

    <com.neganet.QRelations.fragments.SwipeListenerFragment xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent"
    android:id="@+id/main_list_layout"
    android:clickable="true"
    android:focusable="true"
    android:focusableInTouchMode="true"
    android:layout_height="match_parent" tools:context="com.neganet.QRelations.fragments.mainList"
    android:background="@color/main_frag_back">

    <!-- TODO: Update blank fragment layout -->
    <android.support.v7.widget.RecyclerView
        android:id="@+id/farazList"
        android:scrollbars="horizontal"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_gravity="left|center_vertical" />
</com.neganet.QRelations.fragments.SwipeListenerFragment>

you see that begin tag is the class that we made. now in fragment class:

            View view=inflater.inflate(R.layout.fragment_main_list, container, false);
        SwipeListenerFragment tdView=(SwipeListenerFragment) view;
        tdView.registerToSwipeEvents(this);


and then Implement SwipeListenerFragment.onSwipeEventDetected in it:

        @Override
    public void swipeLeftDetected() {
        Toast.makeText(getActivity(), "left", Toast.LENGTH_SHORT).show();
    }

    @Override
    public void swipeRightDetected() {
        Toast.makeText(getActivity(), "right", Toast.LENGTH_SHORT).show();
    }

It's a little complicated but works perfect :)