Question

任何人都可以为我编写一个简单的例子，关于如何从Activity中更改Fragment中的TextView内容（例如MainActivity.java）？

我已经多次尝试过，我的应用每次都会崩溃我尝试使用我创建的方法通过发布我的错误代码使问题复杂化是没有意义的。

Answer 1

您可以使用接口在活动和片段

之间进行通信

此界面将通过包中的数据通知您的片段更新

public interface UpdateFragmentInterface {
    public void update(Bundle data);
}

此接口用于附加片段时要通知的活动

public interface OnUpdatableFragmentAttached {

    public void onAttach(UpdateFragmentInterface iFace);
    public void onDetach(UpdateFragmentInterface iFace);

}

一些虚拟活动

import android.os.Bundle;
import android.support.v4.app.FragmentActivity;

import java.util.ArrayList;


public class UpdatableActivity extends FragmentActivity implements OnUpdatableFragmentAttached {

    private ArrayList<UpdateFragmentInterface> listOfUpdatableFragments;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        // Do other stuff
        listOfUpdatableFragments = new ArrayList<>();
    }

    private void notifyFragments(){
        String someString = "asda";
        String someKey = "key1234";
        Bundle b = new Bundle();
        b.putString(someKey, someString);

        for(UpdateFragmentInterface fragment : listOfUpdatableFragments){
            fragment.update(b);
        }
    }

    @Override
    public void onAttach(UpdateFragmentInterface iFace) {
        listOfUpdatableFragments.add(iFace);
    }

    @Override
    public void onDetach(UpdateFragmentInterface iFace) {
        listOfUpdatableFragments.remove(iFace);
    }

}

还有一些虚拟片段

import android.app.Activity;
import android.os.Bundle;
import android.support.v4.app.Fragment;

    public class UpdatableFragment extends Fragment implements UpdateFragmentInterface {

        @Override
        public void onAttach(Activity activity) {
            super.onAttach(activity);
            if(activity instanceof OnUpdatableFragmentAttached){
                ((OnUpdatableFragmentAttached) activity).onAttach(this);
            }
        }

        @Override
        public void onDetach() {
            super.onDetach();
            if(getActivity() instanceof OnUpdatableFragmentAttached){
                ((OnUpdatableFragmentAttached) getActivity()).onDetach(this);
            }
        }

        @Override
        public void update(Bundle data) {
            // Do something with the data
            String result = data.getString("key1234");
        }
    }

Answer 2

我只使用像Otto这样的事件总线。

public enum SingletonBus {
    INSTANCE;

    private Bus bus;

    private SingletonBus() {
        this.bus = new Bus(ThreadEnforcer.ANY);
    }

    public Bus getBus() {
        return bus;
    }
}

然后

public class MainActivity extends ActionBarActivity {
     @Override
     public void onCreate(Bundle saveInstanceState) {
          super.onCreate(saveInstanceState);
          //do whatever
     }

     @Override
     public void onResume() {
          super.onResume();
          SingletonBus.INSTANCE.getBus().register(this);
     }

     @Override
     public void onPause() {
          SingletonBus.INSTANCE.getBus().unregister(this);
          super.onPause();
     }

     @Override
     public void onPostResume() { //using this to send event only for sake of example
         SingletonBus.INSTANCE.getBus().post(new TextViewChangeEvent("hello world!"));
     }
}

和

public class HomeFragment extends Fragment {
     @InjectView(R.id.your_text_view)
     public TextView yourTextView;


     @Override
     public void onCreateView(LayoutInflater inflater, ViewGroup container, Bundle saveInstanceState) {
          View view = inflater.inflate(R.layout.your_fragment_layout, container, false);
          ButterKnife.inject(this, view);
          //do whatever
          return view;
     }

     @Override
     public void onResume() {
          super.onResume();
          SingletonBus.INSTANCE.getBus().register(this);
     }

     @Override
     public void onPause() {
          SingletonBus.INSTANCE.getBus().unregister(this);
          super.onPause();
     }

     @Subscribe
     public void onTextViewChangeEvent(TextViewChangeEvent e) {
          this.yourTextView.setText(e.getText());
     }
}

与

public class TextViewChangeEvent {
     private String text;

     public TextViewChangeEvent(String text) {
          this.text = text;
     }

     public String getText() {
          return text;
     }
}

从活动中更改片段中的textView的简单示例

2 个答案: