单击后退按钮两次时，关闭应用程序

Question

My Activity flow looked like this

LogIn Activity-> Activity A(Main Page)->Activity B-> Activity C

When button in C is clicked, it will intent to A.

When back button in A is pressed twice,it should close the app.

  boolean doubleBackToExitPressedOnce = false;
     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;
                    Intent a = new Intent(Intent.ACTION_MAIN); // close app code
                    a.addCategory(Intent.CATEGORY_HOME);
                    a.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
                    startActivity(a);
                }
            },2000);

Problem :

when I press the button one times, it will display Please click BACK again to exit , and then it will close the app automatically even I didn't clicked the button twice.

If I click the button twice, it will back to LogIn Activity. What is the correct way to write ? Thanks

Edit

If I remove the intent

 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);


    }

When double click the back button, it will back to Activity C again.

Answer 1

maybe just use long lastTimePressed=0L; and store in it System.currentTimeMillis(); and if(System.currentTimeMillis()-lastTimePressed>2000) finish();

2000 for Toast.Length_SHORT , 3500 for Toast.LENGTH_LONG

long lastTimePressed=0L;

@Override
public void onBackPressed (){
    if(System.currentTimeMillis()-lastTimePressed>2000) //short Toast duration, now should be faded out
        finish();
    else
        Toast.makeText(this, "Please click BACK again to exit", Toast.LENGTH_SHORT).show();

    lastTimePressed=System.currentTimeMillis();
}

don't start new Activity (or maybe? if you have implemented singleTask or singleTop or noHistory , but I doubt). finish(); and super.onBackPressed(); do the same practially. possibility for override onBackPressed is added later in API5, because its simply usefull :)

ohh, now I see your edit and everything is clear. Don't start your Activities with startActivity , but with startActivityForResult . Implement also onActivityResult ( check out here ). When you use

private static final int MY_RESULT_IS_KILL_MY_APP=4573; //random

setResult(MY_RESULT_IS_KILL_MY_APP);
finish();

and Activity below receives that in own onActivityResult it should also set this result and call finish(); . This way stack of Activities clean away and entire Application will exit. Without setting this static result finish(); will finish only current Activity

Answer 2

Finish LogIn Activity Before opening Activity A. that's it.

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;
                    MainActivity.this.finish();
                }
            },2000);
        }

Answer 3

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

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

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

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