Java 如何从片段访问活动（mainactivity除外）？

我创建了我的测试项目，在其中我编写代码在两个片段之间通信，但实际上我想从片段中访问活动。 下面是将片段连接到片段的代码，其工作完全正确，没有任何错误，但现在我想将此代码更改为将活动从片段连接到片段，而不是从片段到片段的通信。 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

以下是我的主要活动：

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filters.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);  }
 }

公共类活动{
回收视图mRecyclerView；
列出我的肥料清单；
肥料数据MFF肥料数据；
@凌驾
创建时受保护的void（Bundle savedInstanceState）{
super.onCreate（savedInstanceState）；
setContentView（R.layout.activity_）；
mRecyclerView=（RecyclerView）findViewById（R.id.RecyclerView）；
GridLayoutManager GridLayoutManager；
gridLayoutManager=新的gridLayoutManager（1.this，1）；
mRecyclerView.setLayoutManager（gridLayoutManager）；
MyFertifizersList=新的ArrayList（）；
mFertilizersData=新肥料数据（“尿素肥料”、“尿素是一种肥料”、“Rs.1900”、R.drawable.Urea”）；
MyFertifizersList.add（mFertifizersData）；
MyFertifizersList.add（MFFertifizersData）；}
}

请在这里写一段代码来调用FragmentA中的Fertilezers活动，我将非常感谢您。

在您的片段中调用

getActivity（）

将为您提供调用活动，因此如果

MainActivity

启动了您的片段，那么您就可以这样做

(MainActivity(getActivity())).something_from_your_main_activity

---

关于这个问题，它自己找到了解决办法

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;

}
}

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();
        }

    }
}
}

FertifizerSactivity.java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;

}
}

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();
        }

    }
}
}

---

感谢您的真诚关注，@tyczj您能用工作代码块解释一下吗？这样我就能清楚地理解您宝贵的建议。碎片不能“转换”为活动。您需要设置一个从片段B到活动的回调，然后从活动到片段a调用一个（公共）方法，这在您的代码中似乎是这样。如果我创建一个新的活动名称作为FertizerSactivity，那么如何从片段a访问呢？请查看您自己的代码。使用fragmentA=new fragmentA（）创建片段A，以便以后可以使用fragmentA.YourMethod（）调用其方法（如果是公共的）；