How onResume() working in android

Question

Hi for me one doubt if I change any content or color of activity example, in activity1 I have one textview with data "apple" from shared preference. And I am clicking a button to start new activity2 there I am clicking one button to update the shared preference "apple" to "gova" I click back button of activity2 textview in activity should update. Is there any way to update without onResume() method or explain how onResume() working...?

Answer 1

onResume() is called every time your activity is shown to the user. Thus, if the user goes to another activity and then comes back to the first one, onResume() will be called. Your code should look like:

@Override
protected void onResume() {
    super.onResume();
    myTextView.setText(preferences.getString("myKey", "defaultValue");
}

If, for any reason, you'd prefer not to use onResume(), you can register a OnSharedPreferenceChangeListener, which will be called every time a shared pref value is changed.

Your first activity will include code that looks like this:

public class MainActivity extends AppCompatActivity {

SharedPreferences preferences;
SharedPreferences.OnSharedPreferenceChangeListener listener;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main_layout);

    preferences = PreferenceManager.getDefaultSharedPreferences(this);
    listener = new SharedPreferences.OnSharedPreferenceChangeListener() {
        @Override
        public void onSharedPreferenceChanged(SharedPreferences sharedPreferences, String key) {
            if (key.equals("myKey")) {
                // update your textview
            }
        }
    };
    preferences.registerOnSharedPreferenceChangeListener(listener);
}

@Override
protected void onDestroy() {
    super.onDestroy();
    preferences.unregisterOnSharedPreferenceChangeListener(listener);
}
}

Answer 2

Just override onBackPressed method in second activity and in it set the value to shared preferences :

@Override
public void onBackPressed() {
    // Set shared preference value
}

Answer 3

You should ideally use onBackPressed instead on onResume. Below is a code snippet on similar lines that should help

@Override
public void onBackPressed() {
new AlertDialog.Builder(this)
    .setTitle("Really go back?")
    .setMessage("Are you sure you want to?")
    .setNegativeButton(android.R.string.no, null)
    .setPositiveButton(android.R.string.yes, new OnClickListener() {

        public void onClick(DialogInterface arg0, int arg1) {
            Activity1.super.onBackPressed();
            //change sharedPreferences here
        }
    }).create().show();
}

Hope this helps