如何在我的应用程序中实现后退按钮手势

Question

As we know from android OS version 4.1 there is a new feature to add a back button gesture for the device. I want to use this back button gesture from my application. How to do that programmatically?

Answer 1

You can implement gesture in application programmatically and on particular gesture event you can call onBackPressed(); method of activity. This way you will able to achieve back button gesture in your application.

import android.view.GestureDetector;
import android.view.GestureDetector.SimpleOnGestureListener;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnTouchListener;

public class OnSwipeTouchListener implements OnTouchListener {

private final GestureDetector gestureDetector;

public OnSwipeTouchListener (Context ctx){
    gestureDetector = new GestureDetector(ctx, new GestureListener());
}

private final class GestureListener extends SimpleOnGestureListener {

    private static final int SWIPE_THRESHOLD = 100;
    private static final int SWIPE_VELOCITY_THRESHOLD = 100;

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

    @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)) {
                if (Math.abs(diffX) > SWIPE_THRESHOLD && Math.abs(velocityX) > SWIPE_VELOCITY_THRESHOLD) {
                    if (diffX > 0) {
                        onSwipeRight();
                    } else {
                        onSwipeLeft();
                    }
                }
            } else {
                if (Math.abs(diffY) > SWIPE_THRESHOLD && Math.abs(velocityY) > SWIPE_VELOCITY_THRESHOLD) {
                    if (diffY > 0) {
                        onSwipeBottom();
                    } else {
                        onSwipeTop();
                    }
                }
            }
        } catch (Exception exception) {
            exception.printStackTrace();
        }
        return result;
    }
}

public void onSwipeRight() {
    onBackPressed();
}

public void onSwipeLeft() {
    onBackPressed();
}

public void onSwipeTop() {
    onBackPressed();
}

public void onSwipeBottom() {
    onBackPressed();
}
}

Let me know if you face any issue.

Answer 2

You don't have to worry about that. If the user has this accessibility feature enabled, when he/she does the gesture, android will automatically simulate a back button press.

I might have completely misunderstood your question, in which case you should consider revising.