Android: Simulate the back button twice

Question

I have a situation where I have a three step registration process. Each step is contained in its own activity - call them A, B, and C. Only when I get to the end of step three, can I reliably validate one of the inputs (and email address to which I send a confirmation using PHPMailer). If this comes back with an error, I want to go all the way back to A, which is where the email address is entered.

This is easy enough by just calling an Intent. However, I want to retain the input values that the user entered originally so that they don't have to enter them again. Theoretically, the easiest way to do this is to call finish() twice. But this doesn't work since calling it once transfers control back to B and the second call never happens.

Is there a simple way to do this, or do I have to call Intent and then somehow populate the fields through another method? Thanks!

Answer 1

I'm not sure I completely get you but you could use the flag FLAG_ACTIVITY_CLEAR_TOP to bring it back to A and remove B.

Intent i = new Intent(C.this, A.class)
i.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
startActivity(i);
finish();

Run this code when you get the error and it will bring A back up. And if the "Back" button is pressed you will still get to B.

Another option you have is to store the information in something like SharedPreferences and load the data from there but this may be unnecessary for your situation.

Answer 2

To pass data around between activities, use a Bundle, for an example, in this class activity - B

Intent intent = new Intent(this, C.class);
Bundle b = new Bundle();
b.putBoolean("some_boolean_value", true);
b.putInt("some_int_value", 4);
b.putString("some_string_value", "foobar");
intent.putExtra("fooBundle", b);
intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK | Intent.FLAG_ACTIVITY_CLEAR_TOP);
startActivity(i);
finish();

Then, from your class activity 'C', after it appears on screen, from within the onCreate method, extract the bundle:

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    if (savedInstanceState.containsKey("fooBundle")){
        Bundle b = savedInstanceState.getBundle("fooBundle");
        int nVal = b.getInt("some_int_value");
        String sVal = b.getString("some_string_value");
        boolean blnVal = b.getBoolean("some_boolean_value");
        // Do whatever you have to do, put them into textview's etc.
    }
}

Notice, how the check is made to ensure there is indeed a bundle, if not, its an "empty view" i.e. no data to prefill into the fields. And reverse the pulling out the values from the Bundle.

When you back out of the class activity C, it goes back to activity A.

Edit

The OP is insistent on using "two" back key strokes which is deemed unnecessary as the flag indicating the activity is cleared from the stack.

A -> B

Before creating the intent in the above code and runs, the stack now becomes...

A -> C

Now back out of the activity C, by pressing the back key.

A