Using Fling Motion Gesture in Android

The layout .

I’m using the ViewFlipper to demonstrate this simple fling application.

So, what is Fling… It’s also known as the swiping action on your mobile device screen.

In this demo, I prepared an Activity with ViewFlipper layout that has 3 screens. Green, Blue and Yellow.

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    >
    <TableLayout android:id="@+id/LinearLayout01" 
        android:layout_width="fill_parent" 
        android:layout_height="wrap_content">
        <TableRow>
            <TextView android:id="@+id/btnback"
                android:text="Fling left - Back  "
                android:layout_width="fill_parent"
                android:layout_height="wrap_content"/>
            <TextView android:id="@+id/btnforward"
                android:text="  Fling right - Forward"
                android:layout_width="fill_parent"
                android:layout_height="wrap_content"/>
        </TableRow>
    </TableLayout>
    <ViewFlipper
        android:id="@+id/pages"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent" >
        <TextView
            android:text="1.red"
            android:layout_width="fill_parent"
            android:layout_height="fill_parent"
            android:background="#AAff0000" />
        <TextView
            android:text="2.green"
            android:layout_width="fill_parent"
            android:layout_height="fill_parent" 
            android:background="#AA00ff00" />
        <TextView
            android:text="3.blue"
            android:layout_width="fill_parent"
            android:layout_height="fill_parent"
            android:background="#AA0000ff"  />
    
    </ViewFlipper>
</LinearLayout>

The Code…

package com.kerul.FlipperFling;
import android.app.Activity;
import android.os.Bundle;
import android.view.GestureDetector;
import android.view.MotionEvent;
import android.view.GestureDetector.OnGestureListener;
import android.widget.Toast;
import android.widget.ViewFlipper;
public class FlipperFling extends Activity implements OnGestureListener {
	protected GestureDetector gestureScanner;
	protected ViewFlipper vf;
	private static final int SWIPE_MIN_DISTANCE = 120;
    private static final int SWIPE_MAX_OFF_PATH = 250;
    private static final int SWIPE_THRESHOLD_VELOCITY = 200;
	@Override
	public void onCreate(Bundle savedInstanceState){
		super.onCreate(savedInstanceState);
		gestureScanner = new GestureDetector(this);
		setContentView(R.layout.main);
        vf = (ViewFlipper) findViewById(R.id.pages);
	}
	@Override
	public boolean onTouchEvent(MotionEvent me){
		return gestureScanner.onTouchEvent(me);
	}
	public boolean onDown(MotionEvent e){
		return true;
	}
	public boolean onFling(MotionEvent e1,MotionEvent e2,float velocityX,float velocityY){
		try {
            if(e1.getX() > e2.getX() && Math.abs(e1.getX() - e2.getX()) > SWIPE_MIN_DISTANCE && Math.abs(velocityX) > SWIPE_THRESHOLD_VELOCITY) {
                Toast.makeText(this.getApplicationContext(), "Left", Toast.LENGTH_SHORT).show();
                vf.showPrevious();
            }else if (e1.getX() < e2.getX() && e2.getX() - e1.getX() > SWIPE_MIN_DISTANCE && Math.abs(velocityX) > SWIPE_THRESHOLD_VELOCITY) {
                Toast.makeText(this.getApplicationContext(), "Right", Toast.LENGTH_SHORT).show();
                vf.showNext();
            }
        } catch (Exception e) {
            // nothing
        }
        return true;
		
	}
	public void onLongPress(MotionEvent e){}
	
	public boolean onScroll(MotionEvent e1,MotionEvent e2,float distanceX,float distanceY){
		return true;
	}
	public void onShowPress(MotionEvent e){}
	public boolean onSingleTapUp(MotionEvent e){ return true;}
}

Focus on onFling method, the fling gesture is detected in the method. (I’ll explain later…).

The onFling method (which is the method detecting the Fling motion will catch a horizontal swipe, either from left to right, or from right to left). Assuming that MotionEvent.e1 is the starting point of the motion, and MotionEvent.e2 is the end. FYI the screen coordinate (0,0) starts from the top-left corner.  So left to right motion detected when the e1.getX is greater than e2.getX, and vice-versa.