ViewPager中Fragment之间的通信 [英] Communication between Fragments in ViewPager

问题描述

我正在尝试这样做:http://android-er.blogspot.com/2012/06/communication-between-fragments-in.html除了我使用的是 FragmentStatePagerAdapter

I'm trying to do this: http://android-er.blogspot.com/2012/06/communication-between-fragments-in.html Except that I'm using a FragmentStatePagerAdapter

我有一个带有两个片段的 Activity(FragmentA & FragmentB)

I have an Activity with two fragments(FragmentA & FragmentB)

FragmentA 有一个编辑文本和一个按钮，FragmentB 有一个文本视图

FragmentA has an edittext and a button, FragmentB has a textview

现在我想要的是，每当我在编辑文本中输入内容并单击按钮时，文本视图中就会出现一些内容.

Now all I want is that whenever I enter something in the edittext and click the button, that something will appear on my textview.

主要活动:

public class MainActivity extends FragmentActivity {


    ViewPager viewPager = null;
    String TabFragmentB;

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

        viewPager = (ViewPager)findViewById(R.id.pager);    
        FragmentManager fragmentManager = getSupportFragmentManager();
        viewPager.setAdapter(new MyAdapter(fragmentManager));

    }

    public class MyAdapter extends FragmentStatePagerAdapter {  

        public MyAdapter (FragmentManager fm) {
            super(fm);
        }

        @Override
        public Fragment getItem(int i) {
            Fragment fragment = null;

            if (i == 0)
            {
                fragment = new FragmentA();
            }
            if (i == 1)
            {
                fragment = new FragmentB();
            }
            return fragment;
        }

        @Override
        public int getCount() {
            return 2;
        }   
    }

    public void setTabFragmentB(String t) {
        TabFragmentB = t;   
    }

    public String getTabFragmentB() { 
        return TabFragmentB;
    }

}

片段A:

public class FragmentA extends Fragment {

    EditText et;
    Button bt;

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {

        View v = inflater.inflate(R.layout.fraga, container, false);

        et = (EditText)v.findViewById(R.id.edit1);
        bt = (Button)v.findViewById(R.id.button1);
        bt.setOnClickListener(Click);

        return v;
    }

    OnClickListener Click = new OnClickListener(){

        @Override
        public void onClick(View v) {

            String textPassToB = et.getText().toString();

            String TabOfFragmentB = ((MainActivity)getActivity()).getTabFragmentB();

            FragmentB fragmentB = (FragmentB)getActivity()
               .getSupportFragmentManager()
               .findFragmentByTag(TabOfFragmentB);

            fragmentB.updateText(textPassToB);          
        }   
    };

}

片段B:

public class FragmentB extends Fragment {

    TextView tv;

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {

        View v = inflater.inflate(R.layout.fragb, container, false);    

        tv = (TextView)v.findViewById(R.id.text1);
        String myTag = getTag();

        ((MainActivity)getActivity()).setTabFragmentB(myTag);

        return v;
    }

    public void updateText(String t){
          tv.setText(t);
         }

}

LogCat:

FATAL EXCEPTION: main
 java.lang.NullPointerException
        at lmf.sample1.FragmentA$1.onClick(FragmentA.java:43)
        at android.view.View.performClick(View.java:4212)
        at android.view.View$PerformClick.run(View.java:17476)
        at android.os.Handler.handleCallback(Handler.java:800)
        at android.os.Handler.dispatchMessage(Handler.java:100)
        at android.os.Looper.loop(Looper.java:194)
        at android.app.ActivityThread.main(ActivityThread.java:5371)
        at java.lang.reflect.Method.invokeNative(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:525)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:833)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:600)
        at dalvik.system.NativeStart.main(Native Method)

每当我点击第一个片段上的按钮时，我的应用就会崩溃.到底是什么问题?

Whenever I click the button on my first fragment, my app crashes. What the hell is the problem?

推荐答案

1. 您可以使用意图(在片段 B 中注册广播接收器并从片段 A 发送广播.
2. 使用 EventBus:https://github.com/greenrobot/EventBus.这是我最喜欢的方法.使用起来非常方便，任何组件(例如活动和服务)之间的通信都很容易.

1. You could use Intents (register broadcast receiver in fragment B and send broadcasts from fragment A.
2. Use EventBus: https://github.com/greenrobot/EventBus. It's my favorite approach. Very convinient to use, easy communications between any components (Activity & Services, for example).

要做的步骤:

首先，创建一些类来表示文本更改时的事件:

First, create some class to represent event when your text changes:

public class TextChangedEvent {
  public String newText;
  public TextChangedEvent(String newText) {
      this.newText = newText;
  }
}

然后，在片段 A 中:

Then, in fragment A:

//when text changes
EventBus bus = EventBus.getDefault();
bus.post(new TextChangedEvent(newText));

在片段 B 中:

EventBus bus = EventBus.getDefault();

//Register to EventBus
@Override
public void onCreate(SavedInstanceState savedState) {
 bus.register(this);
}

//catch Event from fragment A
public void onEvent(TextChangedEvent event) {
 yourTextView.setText(event.newText);
}

这篇关于ViewPager中Fragment之间的通信的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！