Android Studio：在活动中调用“finish()”后，前一屏幕中的代码无法继续

Question

I'm new to Android Development and am trying to make a simple habit tracking app. The initial screen is a fragment called HabitFragment. It has a button that, when clicked, takes the user to an activity, called HabitDialogueActivity, where they create a new habit that they would like to keep track of. When the "done" button is pressed, I call the "finish()" method. In the app, this takes me back to the original screen. However, my code does not seem to continue as my log entries do not show up.

I have this onClickListener and some code after it, it is inside of my OnCreateView():

Button newHabitButton = view.findViewById(R.id.newHabitButton);
newHabitButton.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            goToDialogue();
        }
    });
if (HabitDialogueActivity.getHabitListSize() > habitListSize) {
    Log.d("TAG", "adding to linearLayout, am in if statement");
    habitListSize = HabitDialogueActivity.getHabitListSize();
    Habit newHabit = HabitDialogueActivity.habitList.get(habitListSize - 1);
    TextView text = new TextView(this.getContext());
    text.setText(newHabit.habitName);
    text.setLayoutParams(new LinearLayout.LayoutParams(LinearLayout.LayoutParams.MATCH_PARENT, LinearLayout.LayoutParams.WRAP_CONTENT));
    linearLayout.addView(text);
} else {
    Log.d("TAG", "habit list size not changed");
}

and this is my goToDialogue():

private void goToDialogue() {
    Log.d("TAG", "HabitFragment goToDialogue");
    Intent intent = new Intent(HabitFragment.this.getActivity(), HabitDialogueActivity.class);
    startActivity(intent);
}

My HabitDialogueActivity just has a few text fields, an ArrayList of habits, and a "done" button which calls finish(). It takes me back to my HabitFragment, but the Log entries in the if statement that follow the setOnClickListener do not show in the log. Why doesn't the code in HabitFragment continue to execute after I leave HabitDialogueActivity?

I am new to this website, so I'm sorry if I've left anything out.

Answer 1

Put your code inside onResume to rerun it when you go back to previously screen and remove it from on Create View. onResume will run after oncreate when you open the screen for the first time.

Check the docs https://developer.android.com/guide/components/activities/activity-lifecycle

@Override
public void onResume() {
    super.onResume();
    // put your code here...
    if (HabitDialogueActivity.getHabitListSize() > habitListSize) {
        Log.d("TAG", "adding to linearLayout, am in if statement");
        habitListSize = HabitDialogueActivity.getHabitListSize();
        Habit newHabit = HabitDialogueActivity.habitList.get(habitListSize - 1);
        TextView text = new TextView(this.getContext());
        text.setText(newHabit.habitName);
        text.setLayoutParams(new LinearLayout.LayoutParams(LinearLayout.LayoutParams.MATCH_PARENT, LinearLayout.LayoutParams.WRAP_CONTENT));
        linearLayout.addView(text);
    } else {
        Log.d("TAG", "habit list size not changed");
    }
}

Answer 2

OnCreateView is only called when the Fragment is created. Since it wasn't destroyed when you navigated to the HabitDialogueActivity , OnCreateView isn't called again.

You can move your if statement inside the Fragment's onResume() method in order to check if new data is available each time you navigate back to the activity to which the Fragment is attached.

    @Override
    public void onResume() {
        super.onResume();
        if (HabitDialogueActivity.getHabitListSize() > habitListSize) {
            Log.d("TAG", "adding to linearLayout, am in if statement");
            habitListSize = HabitDialogueActivity.getHabitListSize();
            Habit newHabit = HabitDialogueActivity.habitList.get(habitListSize - 1);
            TextView text = new TextView(this.getContext());
            text.setText(newHabit.habitName);
            text.setLayoutParams(new LinearLayout.LayoutParams(LinearLayout.LayoutParams.MATCH_PARENT, LinearLayout.LayoutParams.WRAP_CONTENT));
            linearLayout.addView(text);
        } else {
            Log.d("TAG", "habit list size not changed");
        }
    }