在动态创建的片段之间进行通信，从而产生空指针exception
我创建了一个ListFragment并在每个项目的ListFragment上尝试将List的值打开到其他Fragment 。
我已经成功创建了两个fragments并通过google docs中描述的活动通过interface进行通信。
但是，当我尝试在每个项目单击列表上创建一个新Fragment并通过接口进行通信时，我在该视图上获得Null Pointer Exception
public class Details extends Fragment { ViewGroup view_details; static int count; @Override public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { view_details = (ViewGroup) inflater.inflate( R.layout.details, container , false); return view_details; } public void setTextView(String details_string){ Log.d("TAG", ""+details_string.toString()); TextView txt_view_details = (TextView) view_details.findViewById(R.id.txt_details); //Getting Null POinter Here txt_view_details.setText(details_string.toString()); } }
我将新Fragment插入FrameLayout的接口方法是：
@Override public void connectIt(String time) { Details details = new Details(); FragmentTransaction fragmentTransaction = getFragmentManager().beginTransaction(); fragmentTransaction.replace( R.id.frameLayout , details ); fragmentTransaction.addToBackStack(null); if (details != null ) { details.setTextView(time); } fragmentTransaction.commit(); } 12-17 18:18:06.740: E/AndroidRuntime(15917): FATAL EXCEPTION: main 12-17 18:18:06.740: E/AndroidRuntime(15917): java.lang.NullPointerException 12-17 18:18:06.740: E/AndroidRuntime(15917): at com.raweng.fragmentdemo.Details.setTextView(Details.java:31) 12-17 18:18:06.740: E/AndroidRuntime(15917): at com.raweng.fragmentdemo.FragmentDemo.connectIt(FragmentDemo.java:46) 12-17 18:18:06.740: E/AndroidRuntime(15917): at com.raweng.fragmentdemo.ListData.updateIt(ListData.java:41) 12-17 18:18:06.740: E/AndroidRuntime(15917): at com.raweng.fragmentdemo.ListData.onListItemClick(ListData.java:34) 12-17 18:18:06.740: E/AndroidRuntime(15917): at android.app.ListFragment$2.onItemClick(ListFragment.java:160) 12-17 18:18:06.740: E/AndroidRuntime(15917): at android.widget.AdapterView.performItemClick(AdapterView.java:298) 12-17 18:18:06.740: E/AndroidRuntime(15917): at android.widget.AbsListView.performItemClick(AbsListView.java:1128) 12-17 18:18:06.740: E/AndroidRuntime(15917): at android.widget.AbsListView$PerformClick.run(AbsListView.java:2812) 12-17 18:18:06.740: E/AndroidRuntime(15917): at android.widget.AbsListView$1.run(AbsListView.java:3571) 12-17 18:18:06.740: E/AndroidRuntime(15917): at android.os.Handler.handleCallback(Handler.java:725) 12-17 18:18:06.740: E/AndroidRuntime(15917): at android.os.Handler.dispatchMessage(Handler.java:92) 12-17 18:18:06.740: E/AndroidRuntime(15917): at android.os.Looper.loop(Looper.java:153) 12-17 18:18:06.740: E/AndroidRuntime(15917): at android.app.ActivityThread.main(ActivityThread.java:5297) 12-17 18:18:06.740: E/AndroidRuntime(15917): at java.lang.reflect.Method.invokeNative(Native Method) 12-17 18:18:06.740: E/AndroidRuntime(15917): at java.lang.reflect.Method.invoke(Method.java:511) 12-17 18:18:06.740: E/AndroidRuntime(15917): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:833) 12-17 18:18:06.740: E/AndroidRuntime(15917): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:600) 12-17 18:18:06.740: E/AndroidRuntime(15917): at dalvik.system.NativeStart.main(Native Method)
任何帮助都得到了真正的赞赏……
这是因为当你调用details.setTextView（time）时; 片段的视图尚未创建。 你应该把时间作为参数传递给片段。 在您的详细碎片类中创建此方法
public static Detail newInstance(String time) { Detail fragment = new Detail(); Bundle args = new Bundle(); args.putString("time", time); fragment.setArguments(args); return fragment; }
然后你可以花时间在onCreateView中设置它：
@Override public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { view_details = (ViewGroup) inflater.inflate( R.layout.details, container , false); TextView txt_view_details = (TextView) view_details.findViewById(R.id.txt_details); txt_view_details.setText(getArguments().getString("title")); return view_details; }
然后在你的活动中创建这样的片段：
@Override public void connectIt(String time) { Details details = Details.newInstance(time); FragmentTransaction fragmentTransaction = getFragmentManager().beginTransaction(); fragmentTransaction.replace( R.id.frameLayout , details ); fragmentTransaction.addToBackStack(null); fragmentTransaction.commit(); }