如何在片段中保存工具栏的 state？

Question

I am new to android. I got a toolbar with one button in a fragment, when my emulator changes orientation, another button is added. What do I need to fix it?

Answer 1

I found a solution to the problem. Шn the activity to which the fragment is attached in the onCreate(@Nullable Bundle savedInstanceState) , before creating a new transaction, you must check the activity state for null, only then create a transaction and add a fragment. Example:

public abstract class SingleFragmentActivity extends AppCompatActivity {

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_single_fragment);
        if (savedInstanceState == null){
            Fragment fragment = createFragment();
            getSupportFragmentManager().beginTransaction()
                    .add(R.id.fl_single_fragment_container, fragment, fragment.getClass().getSimpleName()).commit();
        }
    }

    abstract Fragment createFragment();
}

more details can be found here: https://developer.android.com/guide/fragments/create#java