Android 片段数组列表nullpointerexception
我仍然是android的初学者,我正在使用listAdapter在UI中实现一个简单的数组列表,但是我在代码中一直遇到这个错误 你能帮我吗 异常堆栈跟踪:Android 片段数组列表nullpointerexception,android,nullpointerexception,fragment,listadapter,Android,Nullpointerexception,Fragment,Listadapter,我仍然是android的初学者,我正在使用listAdapter在UI中实现一个简单的数组列表,但是我在代码中一直遇到这个错误 你能帮我吗 异常堆栈跟踪: android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2693) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2758) at android.app.Act
android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2693)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2758)
at android.app.ActivityThread.access$900(ActivityThread.java:177)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1448)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:145)
at android.app.ActivityThread.main(ActivityThread.java:5942)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1400)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1195)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ListView.setAdapter(android.widget.ListAdapter)' on a null object reference
at test.ahlem.tn.sunshine.PlaceholderFragment.onCreateView(PlaceholderFragment.java:61)
at android.support.v4.app.Fragment.performCreateView(Fragment.java:2080)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1108)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1290)
at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:801)
at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1677)
at android.support.v4.app.FragmentController.execPendingActions(FragmentController.java:388)
at android.support.v4.app.FragmentActivity.onStart(FragmentActivity.java:604)
at android.support.v7.app.AppCompatActivity.onStart(AppCompatActivity.java:178)
at android.app.Instrumentation.callActivityOnStart(Instrumentation.java:1234)
at android.app.Activity.performStart(Activity.java:6329)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2656)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2758)
at android.app.ActivityThread.access$900(ActivityThread.java:177)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1448)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:145)
at android.app.ActivityThread.main(ActivityThread.java:5942)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1400)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1195) <p>
android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2693)
在android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2758)上
在android.app.ActivityThread.access$900(ActivityThread.java:177)
在android.app.ActivityThread$H.handleMessage(ActivityThread.java:1448)
位于android.os.Handler.dispatchMessage(Handler.java:102)
位于android.os.Looper.loop(Looper.java:145)
位于android.app.ActivityThread.main(ActivityThread.java:5942)
位于java.lang.reflect.Method.invoke(本机方法)
位于java.lang.reflect.Method.invoke(Method.java:372)
在com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run上(ZygoteInit.java:1400)
位于com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1195)
原因:java.lang.NullPointerException:尝试在空对象引用上调用虚拟方法“void android.widget.ListView.setAdapter(android.widget.ListAdapter)”
位于test.ahlem.tn.sunshine.PlaceholderFragment.onCreateView(PlaceholderFragment.java:61)
位于android.support.v4.app.Fragment.performCreateView(Fragment.java:2080)
位于android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1108)
位于android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1290)
位于android.support.v4.app.BackStackRecord.run(BackStackRecord.java:801)
位于android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1677)
位于android.support.v4.app.FragmentController.ExecutPendingActions(FragmentController.java:388)
位于android.support.v4.app.FragmentActivity.onStart(FragmentActivity.java:604)
位于android.support.v7.app.AppCompatActivity.onStart(AppCompatActivity.java:178)
位于android.app.Instrumentation.callActivityOnStart(Instrumentation.java:1234)
位于android.app.Activity.performStart(Activity.java:6329)
在android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2656)上
在android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2758)上
在android.app.ActivityThread.access$900(ActivityThread.java:177)
在android.app.ActivityThread$H.handleMessage(ActivityThread.java:1448)
位于android.os.Handler.dispatchMessage(Handler.java:102)
位于android.os.Looper.loop(Looper.java:145)
位于android.app.ActivityThread.main(ActivityThread.java:5942)
位于java.lang.reflect.Method.invoke(本机方法)
位于java.lang.reflect.Method.invoke(Method.java:372)
在com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run上(ZygoteInit.java:1400)
位于com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1195)
占位符片段.java代码:
public class PlaceholderFragment extends Fragment {
public PlaceholderFragment () {
// Required empty public constructor
}
@Override
public void onCreate (Bundle savedInstanceState) {
super.onCreate (savedInstanceState);
}
@Override
public View onCreateView (LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
String[] forcastArray = {
"Today _ sunny _ 88/63",
"Tomorrow _ Foggy _ 70/40",
"wed _ cloudy _ 72/63",
"thus _ Astroids _ 75/65",
"Fri _ heavy Rain _ 65/56",
"SAT _ Help trapped in weatheration _ 60/51",
"sun _ sunny _ 80/68"
};
// Inflate the layout for this fragment
View rootView= inflater.inflate(R.layout.fragment_placeholder, container, false);
List<String> weekForcast = new ArrayList<String> (Arrays.asList (forcastArray));
Log.v ("the weekForcast :", String.valueOf (weekForcast));
ArrayAdapter<String> mForcastAdapter = new ArrayAdapter<String> (getContext(), R.layout.list_item_forcast, weekForcast);
Log.v ("the mForcastAdpter content :", String.valueOf (mForcastAdapter));
ListView listView = (ListView) rootView.findViewById (R.id.listview_forcast);
listView.setAdapter (mForcastAdapter);
return rootView;
}
}
公共类占位符片段扩展片段{
公共占位符片段(){
//必需的空公共构造函数
}
@凌驾
创建时的公共void(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
}
@凌驾
CreateView上的公共视图(布局、充气机、视图组容器、捆绑包保存状态){
字符串[]forcastArray={
“今天阳光明媚”,
“明天有雾”,
“周三多云,72/63”,
“因此uu75/65”,
“周五-大雨-65/56”,
“SAT uu帮助困在风雨中uuu 60/51”,
“阳光明媚80/68”
};
//为该碎片膨胀布局
视图根视图=充气机。充气(R.layout.fragment\u占位符,容器,false);
List weekForcast=newarraylist(Arrays.asList(forcastArray));
Log.v(“weekForcast:,String.valueOf(weekForcast));
ArrayAdapter mForcastAdapter=新的ArrayAdapter(getContext(),R.layout.list_item_forcast,weekForcast);
Log.v(“mForcastAdapter内容:”,String.valueOf(mForcastAdapter));
ListView ListView=(ListView)rootView.findViewById(R.id.ListView\u forcast);
listView.setAdapter(MForCasAdapter);
返回rootView;
}
}
异常堆栈跟踪显示:
由以下原因引起:java.lang.NullPointerException:尝试在空对象引用上调用虚拟方法“void android.widget.ListView.setAdapter(android.widget.ListAdapter)”
这意味着fragment\u placeholder.xml
布局代码上没有listview\u forcast
id
您可能有一个类型,或者使用了错误的布局。您是否也可以发布片段布局xml?是否尝试进行搜索?在“onCreateView”中有大量关于NPE的问题可能与
<android.support.v7.widget.ListViewCompat
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="@+id/listview_forcast">
</android.support.v7.widget.ListViewCompat>