传递数据beetwen在viewpager片段 [英] Passing data beetwen fragments in viewpager

问题描述

我已经Viewpager机智2片段： CurrentWeatherFragment 和 ForecastFragment 。我需要从一个传递到另一个字符串，用荫像下面的界面，但我不断收到 NullPointerException异常，消息不传递propertly ...

I've Viewpager wit 2 fragments: CurrentWeatherFragment and ForecastFragment. I need to pass string from one to another, Iam using interface like below, but I keep getting NullPointerException, the message is not passing propertly...

public class CurrentWeatherFragment extends Fragment {

SendMessage SM

public void onCreateView(...) {
String Message = "Hello"
SM.sendData(Message);
}

interface SendMessage
{
    public  void sendData(String message);
}

@Override
public void onAttach(Activity activity) {
    super.onAttach(activity);

    try {
        SM = (SendMessage) activity;
    } catch(ClassCastException e) {
        throw  new ClassCastException("Musisz zaimplementowac metode sendData");
    }
}
}

MainActivity.java

MainActivity.java

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


public class MainActivity extends FragmentActivity implements CurrentWeatherFragment.SendMessage {

ViewPager viewPager;


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

    //setting fragment view pager
    viewPager = (ViewPager)findViewById(R.id.pager);
    PagerAdapter pagerAdapter = new PagerAdapter(getSupportFragmentManager());
    viewPager.setAdapter(pagerAdapter);
}

public void sendData (String message){
    ForecastFragment FF = new ForecastFragment();
    FF.getData(message);
}

}

ForecastFragment.java

ForecastFragment.java

public class ForecastFragment extends Fragment {

public View onCreateView(){
TextView txt = (TextView)v.findViewById(R.id.txt_forecast);
}

public void getData(String message){
        txt.setText(message);
}
}

我用这个方法成功地在其他应用，在那里我在一个活动有2个片段，我可以通过ID叫他们

I've used this method succesfully in other app where I've had 2 fragments in one activity and i could call them by ID

public void sendData(String message) {

    SecondFragment f2 = (SecondFragment)getFragmentManager().findFragmentById(R.id.F2);
    f2.getData(message);
}

但这里片段不要有标识，我想是不是通过了消息，因为我不使用 FragmentManager（），但如何找到viewpager片段没有ID，任何建议/想法？

But here Fragments dont have IDs and I think that message is not passed because i dont use FragmentManager(), but how to find fragment in viewpager without ID, any suggestion/ideas?

推荐答案

虽然有点哈克你可以做的是使用下面的code。通过它的标签获得的片段：

Although a little hacky what you can do is get the fragment by its tag by using the following code:

String tag = "android:switcher:" + R.id.pager + ":" + index;
Fragment f = getSupportFragmentManager().findFragmentByTag(tag);

在哪里R.id.pager是在布局和索引viewpager的ID在Viewpager适配器的位置（整数）。
我不能说这将永远工作，但它的那一刻我的作品。

Where R.id.pager is the id of the viewpager in your layout and index is the position (as an integer) in the Viewpager Adapter. I can't say this will work forever but it works for me at the moment.

另类，我会使用一个LocalBroadcastManager和BroadcastReciver因为虽然你的片段之间在内部发送的数据表明其多一点工作，它有助于摆脱你最终可能会发现自己在试图意大利面条code局面直接引用片段。

The Alternative i would suggest is using a LocalBroadcastManager and a BroadcastReciver to send data internally between your fragments as although its a little more work it helps get rid of the spaghetti code situation you may end up finding yourself in trying to reference the fragments directly.

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