Java Bundle Bundle=getArguments()无理由返回null
我正面临一个让我发疯的问题,我只想在列表之间传递一个值,当我点击列表中的一个项目时,我想将Java Bundle Bundle=getArguments()无理由返回null,java,android,Java,Android,我正面临一个让我发疯的问题,我只想在列表之间传递一个值,当我点击列表中的一个项目时,我想将位置发送到另一个列表,所以我使用了bundle,它对我很有效,但当我改进我的应用程序,使用ViewPager和TabsPagerAdapter,而不是旧的选项卡时,在我所做的所有更改之后,出现了一个NullPointerException,尤其是在行中 int-SelectedID=bundle.getInt(“SelectedID”,0) 请注意,getArguments()返回null 这是我的密码:
位置
发送到另一个列表,所以我使用了bundle,它对我很有效,但当我改进我的应用程序,使用ViewPager
和TabsPagerAdapter
,而不是旧的选项卡时,在我所做的所有更改之后,出现了一个NullPointerException
,尤其是在行中
int-SelectedID=bundle.getInt(“SelectedID”,0)代码>
请注意,getArguments()
返回null
这是我的密码:
在我点击列表之前,应用程序工作正常
class WorkoutsFragment extends ListFragment :
@Override
public void onListItemClick(ListView l, View v, int position, long id) {
// TODO Auto-generated method stub
super.onListItemClick(l, v, position, id);
WorkoutListFragment workoutListFrag = new WorkoutListFragment();
Bundle bundle = new Bundle();
//WorkoutID.get() to get the real position from database and it works
bundle.putInt("selectedID", WorkoutID.get(position));
workoutListFrag.setArguments(bundle);
Toast.makeText(getActivity(), "l Position "+WorkoutID.get(position), Toast.LENGTH_SHORT).show();
mCallback.onSwitchToNextFragment();
// Set the item as checked to be highlighted when in two-pane layout
list.setItemChecked(position, true);
}
WorkoutListFragment扩展了ListFragment
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// TODO Auto-generated method stub
View v = inflater.inflate(R.layout.fragment_list, container, false);
// connect object of listview and listview id on xml
list = (ListView) v.findViewById(android.R.id.list);
wla = new WorkoutListAdapter(getActivity());
// get value that passed from previous page
//getArguments() returns null, i don't know why
Bundle bundle = getArguments();
//here is the line of NullPointerException
int SelectedID = bundle.getInt("selectedID",0);
// call asynctask class to get data from database
new getWorkoutList().execute();
}
日志
01-12 11:29:44.048: E/AndroidRuntime(2404): FATAL EXCEPTION: main
01-12 11:29:44.048: E/AndroidRuntime(2404): java.lang.NullPointerException
01-12 11:29:44.048: E/AndroidRuntime(2404): at com.daily.workout.app.WorkoutListFragment.onCreateView(WorkoutListFragment.java:72)
01-12 11:29:44.048: E/AndroidRuntime(2404): at android.support.v4.app.Fragment.performCreateView(Fragment.java:1460)
01-12 11:29:44.048: E/AndroidRuntime(2404): at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:911)
01-12 11:29:44.048: E/AndroidRuntime(2404): at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1088)
01-12 11:29:44.048: E/AndroidRuntime(2404): at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:682)
01-12 11:29:44.048: E/AndroidRuntime(2404): at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1444)
01-12 11:29:44.048: E/AndroidRuntime(2404): at android.support.v4.app.FragmentManagerImpl.executePendingTransactions(FragmentManager.java:461)
01-12 11:29:44.048: E/AndroidRuntime(2404): at android.support.v4.app.FragmentPagerAdapter.finishUpdate(FragmentPagerAdapter.java:141)
01-12 11:29:44.048: E/AndroidRuntime(2404): at android.support.v4.view.ViewPager.populate(ViewPager.java:1012)
01-12 11:29:44.048: E/AndroidRuntime(2404): at android.support.v4.view.ViewPager.setCurrentItemInternal(ViewPager.java:523)
01-12 11:29:44.048: E/AndroidRuntime(2404): at android.support.v4.view.ViewPager.setCurrentItemInternal(ViewPager.java:495)
01-12 11:29:44.048: E/AndroidRuntime(2404): at android.support.v4.view.ViewPager.dataSetChanged(ViewPager.java:875)
01-12 11:29:44.048: E/AndroidRuntime(2404): at android.support.v4.view.ViewPager$PagerObserver.onChanged(ViewPager.java:2690)
01-12 11:29:44.048: E/AndroidRuntime(2404): at android.database.DataSetObservable.notifyChanged(DataSetObservable.java:37)
01-12 11:29:44.048: E/AndroidRuntime(2404): at android.support.v4.view.PagerAdapter.notifyDataSetChanged(PagerAdapter.java:276)
01-12 11:29:44.048: E/AndroidRuntime(2404): at com.daily.workout.app.adapter.TabsPagerAdapter$1.onSwitchToNextFragment(TabsPagerAdapter.java:44)
01-12 11:29:44.048: E/AndroidRuntime(2404): at com.daily.workout.app.WorkoutsFragment.onListItemClick(WorkoutsFragment.java:108)
01-12 11:29:44.048: E/AndroidRuntime(2404): at android.support.v4.app.ListFragment$2.onItemClick(ListFragment.java:58)
01-12 11:29:44.048: E/AndroidRuntime(2404): at android.widget.AdapterView.performItemClick(AdapterView.java:298)
01-12 11:29:44.048: E/AndroidRuntime(2404): at android.widget.AbsListView.performItemClick(AbsListView.java:1100)
01-12 11:29:44.048: E/AndroidRuntime(2404): at android.widget.AbsListView$PerformClick.run(AbsListView.java:2749)
01-12 11:29:44.048: E/AndroidRuntime(2404): at android.widget.AbsListView$1.run(AbsListView.java:3423)
01-12 11:29:44.048: E/AndroidRuntime(2404): at android.os.Handler.handleCallback(Handler.java:725)
01-12 11:29:44.048: E/AndroidRuntime(2404): at android.os.Handler.dispatchMessage(Handler.java:92)
01-12 11:29:44.048: E/AndroidRuntime(2404): at android.os.Looper.loop(Looper.java:137)
01-12 11:29:44.048: E/AndroidRuntime(2404): at android.app.ActivityThread.main(ActivityThread.java:5041)
01-12 11:29:44.048: E/AndroidRuntime(2404): at java.lang.reflect.Method.invokeNative(Native Method)
01-12 11:29:44.048: E/AndroidRuntime(2404): at java.lang.reflect.Method.invoke(Method.java:511)
01-12 11:29:44.048: E/AndroidRuntime(2404): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
01-12 11:29:44.048: E/AndroidRuntime(2404): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
01-12 11:29:44.048: E/AndroidRuntime(2404): at dalvik.system.NativeStart.main(Native Method)
我解决了这个问题,通过只使用一个实例,我犯了一个错误,我将setArguments
放入了一个实例(WorkoutListFragment w=new WorkoutListFragment()
),并启动了另一个新实例(WorkoutListFragment wo=new WorkoutListFragment()
)这个新Instance是空的,它没有参数,这就是它返回NullPointerException
的原因
还有一件重要的事,你必须把bundle参数直接放在你想要启动的类后面(WorkoutListFragment
),这意味着bundle只能在两个类之间连续存在,我有3个,A将参数从第一个传递到第三个,但它不起作用,第二个类负责启动第三个类(WorkoutListFragment
),因为我使用(ListFragments、ViewPager等),所以我在第二个类中设置了参数 您正在将该片段添加到activity.it中,因为您使用的是TabPagerAdapter
,而它没有使用workoutListFrag
实例,而是WorkoutListFragment
的另一个实例(未设置参数)…您已将某些绑定设置到该片段的正确位置。然后,在调用workoutListFrag.setArguments(bundle)之后,加载对象(片段);您没有对workoutListFrag对象执行任何操作。那次电话之后你在哪里使用它?您需要将它设置为某个地方的下一个片段。如果您显示onSwitchToNextFragment()的代码,那么我们可以回答如何解决它。