如何在底部工作表对话框片段中设置文本按钮？

Question

i have one class for bottomsheetdialog fragment.I looked at many places but I'm confused.i want to change text of button in bottom sheet.i get this error 'android.view.View android.view.View.findViewById(int)' on a null object reference. here are my codes;

 public class MainActivity extends AppCompatActivity {

    @Override
     protected void onCreate(final Bundle savedInstanceState) {

       bottomSheetFragment=new BottomSheetFragment();
       View viewDialog=bottomSheetFragment.getView();
       assert viewDialog != null;
       MaterialButton btn_titresim=viewDialog.findViewById(R.id.btn_titresim);
       btn_titresim.setText("text");
     }
 }

Another class for BottomSheetDialogFragment

public class BottomSheetFragment extends BottomSheetDialogFragment {
public BottomSheetFragment() {}

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
}

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    Objects.requireNonNull(getDialog()).setOnShowListener(dialog -> {

        BottomSheetDialog d = (BottomSheetDialog) dialog;
        View bottomSheetInternal = 
            d.findViewById(com.google.android.material.R.id.design_bottom_sheet);
        assert bottomSheetInternal != null;
        BottomSheetBehavior.from(bottomSheetInternal).setState(BottomSheetBehavior.STATE_EXPANDED);
    });
    return inflater.inflate(R.layout.layout_popup, container, false);
}

}

Answer 1

You can solve this by having a listener interface in your fragment that returns the BottomSheet fragment's View back to your activity, so you can then access the BottomSheetDialogFragment underlying views normally by findViewById() method.

Here I decided to use the Singleton pattern for the BottomSheetDialogFragment to set a listener instance from the activity.

So in your fragment add a listener; it's named below FragmentListener , call the listener callback in onCreateView() or in onViewCreated()

public class BottomSheetFragment extends BottomSheetDialogFragment {

    public BottomSheetFragment() {}

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
    }

    interface FragmentListener {
        void getView(View view);
    }

    static FragmentListener mFragmentListener;

    public static BottomSheetFragment newInstance(FragmentListener listener) {
        mFragmentListener = listener;
        return new BottomSheetFragment();
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        Objects.requireNonNull(getDialog()).setOnShowListener(dialog -> {

            BottomSheetDialog d = (BottomSheetDialog) dialog;
            View bottomSheetInternal = 
                d.findViewById(com.google.android.material.R.id.design_bottom_sheet);
            assert bottomSheetInternal != null;
            BottomSheetBehavior.from(bottomSheetInternal).setState(BottomSheetBehavior.STATE_EXPANDED);
        });

        View view = inflater.inflate(R.layout.layout_popup, container, false);

        // Trigger the listener callback to return the view back to the activity
        // mFragmentListener.getView(view);  // Not working in all devices

        return inflater.inflate(R.layout.layout_popup, container, false);
    }

    @Override
    public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
        // Trigger the listener callback to return the view back to the activity
        mFragmentListener.getView(view);
    }

}

implement the listener by your activity, and change the text in your callback, and instantiate the BottomSheetDialogFragment using the singleton pattern instead.

 public class MainActivity extends AppCompatActivity implements BottomSheetFragment.FragmentListener {

    @Override
     protected void onCreate(final Bundle savedInstanceState)  {

       bottomSheetFragment = BottomSheetFragment.newInstance(this);

     }

    @Override
    public void getView(View view) {
        // Setting the text
        ((MaterialButton) view.findViewById(R.id.btn_titresim)).setText("text");
    }

 }

Wish that solves your problem