How can I program the back button of the mobile to go to the main activity

Question

I'm developing an app where I have a menu with Buttons, and in each Button the user go through Fragments. When I press the back Button of the phone (the first of three buttons of the device, the arrow) it goes to the previous Fragment, but I want to go back to the menuscreen.
How can I program that Button to open the menu activity?

Answer 1

You may try overriding onBackPressed() and then routing all back presses to the menu activity:

@Override
public void onBackPressed() {
    Intent goToMenuActivity = new Intent(getApplicationContext(), YourActivity.class);
    startActivity(goToMenuActivity);
}

Answer 2

When I press the back button of the phone (the first of three buttons of the device, the arrow) it goes to the previous fragment

That means you are using back-stack for your fragments.

First Solution

The simple solution is just removing (not using) back-stack

Second Solution

override OnBackStack then manipulate your activity

@Override
public void onBackPressed() {

   finish();
   startActivity(new Intent(this, MenuActivity.class));

}

Third solution

it requires more effort to implement but you may try. @MaximeJallu solution

1 - Create Interface

    public interface IOnBackPressed {
    /**
     * If you return true the back press will not be taken into account, otherwise the activity will act naturally
     * @return true if your processing has priority if not false
     */
    boolean onBackPressed();
}

2 - Prepare your Activity

  public class MyActivity extends Activity {
    @Override public void onBackPressed() {
    Fragment fragment = getSupportFragmentManager().findFragmentById(R.id.main_container);
       if (!(fragment instanceof IOnBackPressed) || !((IOnBackPressed) fragment).onBackPressed()) {
          super.onBackPressed();
       }
    } ...
}

Finally in your Fragment:

public class MyFragment extends Fragment implements IOnBackPressed{
   @Override
   public boolean onBackPressed() {
       if (myCondition) {
            //action not popBackStack
            return true; 
        } else {
            return false;
        }
    }
}

Answer 3

There is two methods

link this 1

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

2

@Override
    public boolean onKeyDown(int keyCode, KeyEvent event) 
   {
        if ((keyCode == KeyEvent.KEYCODE_BACK)) 
        {
            return false; 
        }
        return super.onKeyDown(keyCode, event);
}