android - 在 FragmentTab 中使用额外 Intent 时出错

Question

这是错误logcat:

01-09 21:44:27.461: E/AndroidRuntime(25935): FATAL EXCEPTION: main
01-09 21:44:27.461: E/AndroidRuntime(25935): java.lang.RuntimeException: Unable to start activity ComponentInfo{xx.xx.xx/xx.xx.xx.Mainclass}: java.lang.NullPointerException
01-09 21:44:27.461: E/AndroidRuntime(25935):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2308)
01-09 21:44:27.461: E/AndroidRuntime(25935):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2358)
01-09 21:44:27.461: E/AndroidRuntime(25935):    at android.app.ActivityThread.access$600(ActivityThread.java:153)
01-09 21:44:27.461: E/AndroidRuntime(25935):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1247)
01-09 21:44:27.461: E/AndroidRuntime(25935):    at android.os.Handler.dispatchMessage(Handler.java:99)
01-09 21:44:27.461: E/AndroidRuntime(25935):    at android.os.Looper.loop(Looper.java:137)
01-09 21:44:27.461: E/AndroidRuntime(25935):    at android.app.ActivityThread.main(ActivityThread.java:5227)
01-09 21:44:27.461: E/AndroidRuntime(25935):    at java.lang.reflect.Method.invokeNative(Native Method)
01-09 21:44:27.461: E/AndroidRuntime(25935):    at java.lang.reflect.Method.invoke(Method.java:511)
01-09 21:44:27.461: E/AndroidRuntime(25935):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:795)
01-09 21:44:27.461: E/AndroidRuntime(25935):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:562)
01-09 21:44:27.461: E/AndroidRuntime(25935):    at dalvik.system.NativeStart.main(Native Method)
01-09 21:44:27.461: E/AndroidRuntime(25935): Caused by: java.lang.NullPointerException
01-09 21:44:27.461: E/AndroidRuntime(25935):    at xx.xx.xx.FragmentTab1.onCreateView(FragmentTab1.java:52)
01-09 21:44:27.461: E/AndroidRuntime(25935):    at android.support.v4.app.Fragment.performCreateView(Fragment.java:1460)
01-09 21:44:27.461: E/AndroidRuntime(25935):    at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:911)
01-09 21:44:27.461: E/AndroidRuntime(25935):    at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1088)
01-09 21:44:27.461: E/AndroidRuntime(25935):    at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:682)
01-09 21:44:27.461: E/AndroidRuntime(25935):    at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1444)
01-09 21:44:27.461: E/AndroidRuntime(25935):    at android.support.v4.app.FragmentActivity.onStart(FragmentActivity.java:551)
01-09 21:44:27.461: E/AndroidRuntime(25935):    at android.app.Instrumentation.callActivityOnStart(Instrumentation.java:1164)
01-09 21:44:27.461: E/AndroidRuntime(25935):    at android.app.Activity.performStart(Activity.java:5114)
01-09 21:44:27.461: E/AndroidRuntime(25935):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2271)
01-09 21:44:27.461: E/AndroidRuntime(25935):    ... 11 more

我以前可以很好地使用代码，但我改用我的应用程序中的选项卡导致了问题。

这是解决问题的代码:

Bundle extras = getActivity().getIntent().getExtras(); 

TextView Title = (TextView) getActivity().findViewById(R.id.tvTitle);

if (extras != null) {
    userName = extras.getString("title");
    Title.setText(userName);
}

Title.setText(userName); 是第 52 行。

Answer 1

首先Title是一个变量，应该写成小写。问题在于 TextView 为 null，因为 getActivity().findViewById(R.id.tvTitle) 每次都返回 null。

相反，您必须在 Fragments onCreateView() 方法期间保存所需的 View ，如下所示:

private TextView textView;

...

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    View v = inflater.inflate(R.layout.yourlayout, container, false);
    textView = (TextView) v.findViewById(R.id.textViewId);

    return v;
}