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Codelaby
Asked: 2020-02-18 06:57:48 +0800 CST 2020-02-18 06:57:48 +0800 CST

Press the back button twice to exit the App on Android

  • 772

Lately the applications that come out, have incorporated the fact of pressing the back button twice físico como virtualto exit the app, showing a message `Press one more time to exit.

I have the following implemented:

In MainActivitymain I declare the canExitAppglobal variable to set if it has ever been pressed.

public class MainActivity extends AppCompatActivity {
...    
private boolean canExitApp = false;
...

And in the method I onBackPressedcheck the state variable if it is a trueit exits the app if it is in it falseshows the message with a toast.

@Override
public void onBackPressed() {
    //super.onBackPressed();
    if (!canExitApp) {
        canExitApp = true;
        Toast.makeText(this, getString(R.string.app_back_pressed_exit), Toast.LENGTH_SHORT).show();

        new Handler().postDelayed(new Runnable() {

            @Override
            public void run() {
                canExitApp = false;
            }
        }, 2000);
    } else {
        super.onBackPressed();
    }
}

It would be allowing the user X seconds to press to exit again.

Right now it only works on activitys.

How can I add support for 'fragments', so that if there are none left on the stack, it detects if it wants to exit altogether?

If I use, for example, a side menu that loads fragments, I navigate between them, taking into account that if there is one in the stack, it will show it, until it reaches 0, I want the double-click to exit to work.

java

4 Answers

  1. Best Answer

    I prefer not to use threads to change a variable, but rather to use time based comparisons System.currentTimeMillis(). The following code gives you 2 seconds to press BACK again

        private static final int INTERVALO = 2000; //2 segundos para salir
    private long tiempoPrimerClick;

    @Override
    public void onBackPressed(){
        if (tiempoPrimerClick + INTERVALO > System.currentTimeMillis()){ 
            super.onBackPressed(); 
            return;
        }else { 
            Toast.makeText(this, "Vuelve a presionar para salir", Toast.LENGTH_SHORT).show(); 
        }        
        tiempoPrimerClick = System.currentTimeMillis();
    }
    • 8

  2. In case someone has this problem in android but with Fragments You just have to check that the stack is empty to proceed to check the double back

    private static long presionado;
@Override
    public void onBackPressed(){
        //Si tiene fragments simplemente ejecuta la pulsación Back normal
        if (fragmentManager.getBackStackEntryCount()>0)
            super.onBackPressed();
        else {
            if (presionado + 2000 > System.currentTimeMillis())
                super.onBackPressed();
            else
                Toast.makeText(this, "Vuelve a presionar para salir", Toast.LENGTH_SHORT).show();
            presionado = System.currentTimeMillis();
        }
    }
    • 3

  3. I just found a library for Presione de nuevo para cerrar: Shutdown library . Its use is so simple that it should only be added in the event onBackPressed:

    Shutdown.now(this);

    It will show the message Press back again to closeand the user has 3 seconds, that if he presses the back button again, the app will close.

    The text can be personalized with:

    Shutdown.now(this,"Pulse otra vez para cerrar");

    Based on the Shutdown library I have created the following class

    import android.app.Activity;
import android.support.annotation.StringRes;
import android.widget.Toast;

public class ExitApp {

    private static long lastClickTime;

    public static void now(Activity ctx, @StringRes int message) {
        now(ctx, ctx.getString(message), 2500);
    }

    public static void now(Activity ctx, @StringRes int message, long time) {
        now(ctx, ctx.getString(message), time);
    }

    public static void now(Activity ctx, String message, long time) {
        if (ctx != null && !message.isEmpty() && time != 0) {
            if (lastClickTime + time > System.currentTimeMillis()) {
                ctx.finish();
            } else {
                Toast.makeText(ctx, message, Toast.LENGTH_SHORT).show();
                lastClickTime = System.currentTimeMillis();
            }
        }
    }

}

    Its use

    ExitApp.now(this, R.string.double_back_pressed);
    • 0

  4. You can try this:

    public void onBackPressed() {
    if (doubleBackToExitPressedOnce) {
        super.onBackPressed();
        return;
}

this.doubleBackToExitPressedOnce = true;
Toast.makeText(this, "Pulsa dos veces para salir", Toast.LENGTH_SHORT).show();

new Handler().postDelayed(new Runnable() {

    @Override
    public void run() {
        doubleBackToExitPressedOnce=false;
    }
}, 2000);
}
    • -1