如何从 Fragment 访问 Activity（mainactivity 除外）？

Question

我创建了我的测试项目，我在其中编写代码以在两个片段之间进行通信，但实际上我想从片段访问活动。 这是将片段连接到片段的代码，它的工作绝对正确，没有任何错误，但现在我想更改此代码以将活动从片段而不是片段到片段通信连接起来。 所以请更改此代码以从片段访问活动。我在这个问题上坚持了一个多星期。所以请大家解决这个问题。

这是我的主要活动：

public class MainActivity extends AppCompatActivity implements FragmentA.FragmentAListener, FragmentB.FragmentBListener {
private FragmentA fragmentA;
private FragmentB fragmentB;

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

    fragmentA = new FragmentA();
    fragmentB = new FragmentB();

    getSupportFragmentManager().beginTransaction()
            .replace(R.id.container_a, fragmentA)
            .replace(R.id.container_b, fragmentB)
            .commit();
}

@Override
public void onInputASent(CharSequence input) {
    fragmentB.updateEditText(input);
}

@Override
public void onInputBSent(CharSequence input) {
    fragmentA.updateEditText(input);
}

这是我的 FragmentA.java：

 public class FragmentA extends Fragment {
private FragmentAListener listener;
private EditText editText;
private Button buttonOk;

public interface FragmentAListener {
    void onInputASent(CharSequence input);
}

@Nullable
@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
    View v = inflater.inflate(R.layout.fragment_a, container, false);

    editText = v.findViewById(R.id.edit_text);
    buttonOk = v.findViewById(R.id.button_ok);
    buttonOk.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            CharSequence input = editText.getText();
            listener.onInputASent(input);
        }
    });

    return v;
}

public void updateEditText(CharSequence newText) {
    editText.setText(newText);
}

@Override
public void onAttach(Context context) {
    super.onAttach(context);
    if (context instanceof FragmentAListener) {
        listener = (FragmentAListener) context;
    } else {
        throw new RuntimeException(context.toString()
                + " must implement FragmentAListener");
    }
}

@Override
public void onDetach() {
    super.onDetach();
    listener = null;
}
}

这是我的 FragmentB.java：

public class FragmentB extends Fragment {
private FragmentBListener listener;
private EditText editText;
private Button buttonOk;

public interface FragmentBListener {
    void onInputBSent(CharSequence input);
}

@Nullable
@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
    View v = inflater.inflate(R.layout.fragment_b, container, false);

    editText = v.findViewById(R.id.edit_text);
    buttonOk = v.findViewById(R.id.button_ok);
    buttonOk.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            CharSequence input = editText.getText();
            listener.onInputBSent(input);
        }
    });

    return v;
}

public void updateEditText(CharSequence newText) {
    editText.setText(newText);
}

@Override
public void onAttach(Context context) {
    super.onAttach(context);
    if (context instanceof FragmentBListener) {
        listener = (FragmentBListener) context;
    } else {
        throw new RuntimeException(context.toString()
                + " must implement FragmentBListener");
    }
}

@Override
public void onDetach() {
    super.onDetach();
    listener = null;
}
 }

这是我想从 FragmentA 访问的 Fertilizers.java 文件：

 public class Fertilizers extends AppCompatActivity {
RecyclerView mRecyclerView;
List<FertilizerData> myFertilizersList;
FertilizerData mFertilizersData;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_fertilizers);

    mRecyclerView = (RecyclerView)findViewById(R.id.recyclerView);


    GridLayoutManager gridLayoutManager;
    gridLayoutManager = new GridLayoutManager(Fertilizers.this, 1);
    mRecyclerView.setLayoutManager(gridLayoutManager);

    myFertilizersList = new ArrayList<>();
  mFertilizersData = new FertilizerData("Urea Fertilizer","Urea is a concent","Rs.1900",R.drawable.urea);
    myFertilizersList.add(mFertilizersData);
  myFertilizersList.add(mFertilizersData);  }
 }

请在这里写一段代码，从 FragmentA 调用 Fertilzers Activity，我会非常感谢你。

Answer 1

在您的片段中调用getActivity() 会为您提供调用活动，因此如果MainActivity 启动您的片段，那么您会这样做

(MainActivity(getActivity())).something_from_your_main_activity

Answer 2

自行找到有关此问题的解决方案。

FragmentHome.java 类应如下所示：

public class FragmentHome extends Fragment  {



private Button button;


public FragmentHome(){

}

public interface OnMessageReadListener
{
    public  void onMessageRead(String message);
}

 @Nullable
@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
    View v = inflater.inflate(R.layout.fragment_home, container, false);

    button = (Button)v.findViewById(R.id.bn);


  button.setOnClickListener(new View.OnClickListener() {
      @Override
      public void onClick(View view) {
          Intent intent = new Intent(getActivity(), Fertilizers.class);
          intent.putExtra("some","  some data");
          startActivity(intent);
      }
  });
    return v;

}
}

FertilizersActivity.java 应该如下所示：

public class Fertilizers extends AppCompatActivity {

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_fertilizers);
    Bundle bundle = getIntent().getExtras();
    if (bundle != null){
        if(bundle.getStringArrayList("some") !=null){
            Toast.makeText(getApplicationContext(),"data:" + bundle.getStringArrayList("some"),Toast.LENGTH_LONG).show();
        }

    }
}
}