How to exit the android application on backpress?

Question

The situation could be like say, I\'ve 5 activities. Say Main activity, Activity 1, Activity 2, Activity 3 and Activity 4.

One can use the Activity 1,2,3 & 4 dir

Answer 1

You need to Override onBackPressed() inside your MainActivity() and use finishAffinity to finish all activities

onBackPressed()

Called when the activity has detected the user's press of the back key.

finishAffinity() : added in API level 16

Finish this activity as well as all activities immediately below it in the current task that have the same affinity.

SAMPLE CODE

@Override
public void onBackPressed() {
  super.onBackPressed();
  ActivityCompat.finishAffinity(MainActivity.this);
}

EDIT

I want that the user should be able to exit it from the Main Activity itself by displaying a simple AlertDialog box.

@Override
public void onBackPressed() {

        AlertDialog.Builder builder = new AlertDialog.Builder(MainActivity.this)
                .setTitle("Alert")
                .setCancelable(false)
                .setMessage("Are your sure want to exit?")
                .setPositiveButton("Yes", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        ActivityCompat.finishAffinity(MainActivity.this);
                    }
                })
                .setNegativeButton("No", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialogInterface, int i) {

                    }
                });

        builder.show();

}

Answer 2

this is commonly used way to exit the app, also i recommend using "nohistory" attribute in manifest for activities other than MainActivity.

boolean doubleBackToExitPressedOnce = false;
@Override
public void onBackPressed() {
    if (doubleBackToExitPressedOnce) {
        super.onBackPressed();
        return;
    }

this.doubleBackToExitPressedOnce = true;
Toast.makeText(this, "Please click BACK again to exit", Toast.LENGTH_SHORT).show();

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

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

}

and for other activities use nohistory method in manifest

     <activity
        android:name="com.omniapay.salesservice.Activities.LoginActivity"
        android:label="LOGIN"
        android:noHistory="true" />

Answer 3

add your MainActivity

@Override
public void onBackPressed() {
finish();
super.onBackPressed();
}

Answer 4

It is a good code practice to write double back press to exit Main Activity.

boolean doubleBackToExitPressedOnce = false;

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

this.doubleBackToExitPressedOnce = true;
Toast.makeText(this, "Please click BACK again to exit", Toast.LENGTH_SHORT).show();

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

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

}