如何在片段中按下后退按钮时显示警告消息

Question

我希望应用程序在用户按下后退按钮时显示警告消息，如果用户 select 是，它将返回。我在导航图片段中。

我在 stack Overflow 中搜索了很多次并尝试过：

@Override
public void onBackPressed() {
    AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());

    builder.setTitle("Save Or Not");
    builder.setMessage("Do you want to save this? ");
    builder.setPositiveButton("Save", new DialogInterface.OnClickListener() {
        public void onClick(DialogInterface dialog, int id) {
            /*Go back:-I dont know how*/
        }
    });
    builder.setNegativeButton("Discard",null);
    builder.show();
}

但是它显示了 giver 错误： 方法未覆盖其超类中的方法

编辑：我想在导航图片段

中设置 onBackPressedListener（手机后退按钮）

Answer 1

在按钮点击监听器中添加这一行MainActivity.super.onBackPressed(); 替换您的 Activity 名称而不是 MainActivity

 builder.setPositiveButton("Save", new DialogInterface.OnClickListener() {
        public void onClick(DialogInterface dialog, int id) {
          dialog.dismiss();
          MainActivity.super.onBackPressed();
         //Replace your Activity name insted of MainActivity
        }
    });

Answer 2

builder.setPositiveButton("Yes", new DialogInterface.OnClickListener() {
                @Override
                public void onClick(DialogInterface dialog, int which) {
                   //Replace Your Own Action Like Adding Toast etc and Also SuperOnbackprssed or any overriden method
                    dialog.cancel();

                }
            });

Answer 3

使用 Fragments 1.1.0（目前处于 alpha 阶段）时，您可以遵循 Provide custom back navigation documentation, which shows how to register an OnBackPressedCallback，它允许您从 Fragment 中注册 onBackPressed() 回调：

public class MyFragment extends Fragment {

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

    // This callback will only be called when MyFragment is at least Started.
    OnBackPressedCallback callback = new OnBackPressedCallback(true /* enabled by default */) {
        @Override
        public void handleOnBackPressed() {
            AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());

            builder.setTitle("Save Or Not");
            builder.setMessage("Do you want to save this? ");
            builder.setPositiveButton("Save", new DialogInterface.OnClickListener() {
            public void onClick(DialogInterface dialog, int id) {
                // Save your content
                save();
                // Then pop
                NavHostFragment.findNavController(MyFragment.this).popBackStack();
            }
            builder.setNegativeButton("Discard",null);
            builder.show();
        });
        }
    });
    requireActivity().getOnBackPressedDispatcher().addCallback(this, callback);
  }
}

如何在片段中按下后退按钮时显示警告消息

How to show warning message when back button is pressed in fragments

android

android-navigation-editor