Android-由以下原因引起：java.lang.NullPointerException:storage==null

“我正在尝试从数据库检索数据并将其添加到我的listAdapter中。listAdapter不为空时，一切正常。然而，当listAdapter为空时，我得到运行时异常。我试了好几个小时，但找不到解决办法。我尝试过的解决方案，如setEmptyView、setEmptyText、throw Exception等。很抱歉，我是编程新手。”

这是我的ListFragment（LecMonFragmentTab.java）：

对数输出

08-07 04:48:19.271: E/AndroidRuntime(25461): FATAL EXCEPTION: main
08-07 04:48:19.271: E/AndroidRuntime(25461): Process: com.example.fyp2, PID: 25461
08-07 04:48:19.271: E/AndroidRuntime(25461): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.fyp2/com.example.fyp2.LecTakeAtt}: java.lang.NullPointerException: storage == null
08-07 04:48:19.271: E/AndroidRuntime(25461):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2195)
08-07 04:48:19.271: E/AndroidRuntime(25461):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
08-07 04:48:19.271: E/AndroidRuntime(25461):    at android.app.ActivityThread.access$800(ActivityThread.java:135)
08-07 04:48:19.271: E/AndroidRuntime(25461):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
08-07 04:48:19.271: E/AndroidRuntime(25461):    at android.os.Handler.dispatchMessage(Handler.java:102)
08-07 04:48:19.271: E/AndroidRuntime(25461):    at android.os.Looper.loop(Looper.java:136)
08-07 04:48:19.271: E/AndroidRuntime(25461):    at android.app.ActivityThread.main(ActivityThread.java:5017)
08-07 04:48:19.271: E/AndroidRuntime(25461):    at java.lang.reflect.Method.invokeNative(Native Method)
08-07 04:48:19.271: E/AndroidRuntime(25461):    at java.lang.reflect.Method.invoke(Method.java:515)
08-07 04:48:19.271: E/AndroidRuntime(25461):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
08-07 04:48:19.271: E/AndroidRuntime(25461):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
08-07 04:48:19.271: E/AndroidRuntime(25461):    at dalvik.system.NativeStart.main(Native Method)
08-07 04:48:19.271: E/AndroidRuntime(25461): Caused by: java.lang.NullPointerException: storage == null
08-07 04:48:19.271: E/AndroidRuntime(25461):    at java.util.Arrays$ArrayList.<init>(Arrays.java:38)
08-07 04:48:19.271: E/AndroidRuntime(25461):    at java.util.Arrays.asList(Arrays.java:155)
08-07 04:48:19.271: E/AndroidRuntime(25461):    at android.widget.ArrayAdapter.<init>(ArrayAdapter.java:128)
08-07 04:48:19.271: E/AndroidRuntime(25461):    at com.example.fyp2.LecMonFragmentTab.onCreate(LecMonFragmentTab.java:43)
08-07 04:48:19.271: E/AndroidRuntime(25461):    at android.support.v4.app.Fragment.performCreate(Fragment.java:1763)
08-07 04:48:19.271: E/AndroidRuntime(25461):    at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:913)
08-07 04:48:19.271: E/AndroidRuntime(25461):    at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1126)
08-07 04:48:19.271: E/AndroidRuntime(25461):    at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:739)
08-07 04:48:19.271: E/AndroidRuntime(25461):    at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1489)
08-07 04:48:19.271: E/AndroidRuntime(25461):    at android.support.v4.app.FragmentActivity.onStart(FragmentActivity.java:548)
08-07 04:48:19.271: E/AndroidRuntime(25461):    at android.app.Instrumentation.callActivityOnStart(Instrumentation.java:1171)
08-07 04:48:19.271: E/AndroidRuntime(25461):    at android.app.Activity.performStart(Activity.java:5241)
08-07 04:48:19.271: E/AndroidRuntime(25461):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2168)
08-07 04:48:19.271: E/AndroidRuntime(25461):    ... 11 more

08-07 04:48:19.271:E/AndroidRuntime（25461）：致命异常：main
08-07 04:48:19.271:E/AndroidRuntime（25461）：进程：com.example.fyp2，PID:25461
08-07 04:48:19.271:E/AndroidRuntime（25461）：java.lang.RuntimeException:无法启动活动组件信息{com.example.fyp2/com.example.fyp2.LecTakeAtt}:java.lang.NullPointerException:存储==null
08-07 04:48:19.271:E/AndroidRuntime（25461）：在android.app.ActivityThread.performLaunchActivity（ActivityThread.java:2195）上
08-07 04:48:19.271:E/AndroidRuntime（25461）：位于android.app.ActivityThread.handleLaunchActivity（ActivityThread.java:2245）
08-07 04:48:19.271:E/AndroidRuntime（25461）：在android.app.ActivityThread.access$800（ActivityThread.java:135）
08-07 04:48:19.271:E/AndroidRuntime（25461）：在android.app.ActivityThread$H.handleMessage（ActivityThread.java:1196）
08-07 04:48:19.271:E/AndroidRuntime（25461）：位于android.os.Handler.dispatchMessage（Handler.java:102）
08-07 04:48:19.271:E/AndroidRuntime（25461）：在android.os.Looper.loop（Looper.java:136）上
08-07 04:48:19.271:E/AndroidRuntime（25461）：位于android.app.ActivityThread.main（ActivityThread.java:5017）
08-07 04:48:19.271:E/AndroidRuntime（25461）：位于java.lang.reflect.Method.Invokenactive（本机方法）
08-07 04:48:19.271:E/AndroidRuntime（25461）：位于java.lang.reflect.Method.invoke（Method.java:515）
08-07 04:48:19.271:E/AndroidRuntime（25461）：在com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run（ZygoteInit.java:779）
08-07 04:48:19.271:E/AndroidRuntime（25461）：位于com.android.internal.os.ZygoteInit.main（ZygoteInit.java:595）
08-07 04:48:19.271:E/AndroidRuntime（25461）：在dalvik.system.NativeStart.main（本机方法）
08-07 04:48:19.271:E/AndroidRuntime（25461）：由以下原因引起：java.lang.NullPointerException:storage==null
08-07 04:48:19.271:E/AndroidRuntime（25461）：位于java.util.Arrays$ArrayList。（Arrays.java:38）
08-07 04:48:19.271:E/AndroidRuntime（25461）：位于java.util.Arrays.asList（Arrays.java:155）
08-07 04:48:19.271:E/AndroidRuntime（25461）：位于android.widget.ArrayAdapter.（ArrayAdapter.java:128）
08-07 04:48:19.271:E/AndroidRuntime（25461）：在com.example.fyp2.LecMonFragmentTab.onCreate（LecMonFragmentTab.java:43）
08-07 04:48:19.271:E/AndroidRuntime（25461）：在android.support.v4.app.Fragment.performCreate（Fragment.java:1763）
08-07 04:48:19.271:E/AndroidRuntime（25461）：在android.support.v4.app.FragmentManagerImpl.moveToState（FragmentManager.java:913）
08-07 04:48:19.271:E/AndroidRuntime（25461）：在android.support.v4.app.FragmentManagerImpl.moveToState（FragmentManager.java:1126）
08-07 04:48:19.271:E/AndroidRuntime（25461）：在android.support.v4.app.BackStackRecord.run（BackStackRecord.java:739）
08-07 04:48:19.271:E/AndroidRuntime（25461）：在android.support.v4.app.FragmentManagerImpl.execPendingActions（FragmentManager.java:1489）
08-07 04:48:19.271:E/AndroidRuntime（25461）：在android.support.v4.app.FragmentActivity.onStart（FragmentActivity.java:548）
08-07 04:48:19.271:E/AndroidRuntime（25461）：在android.app.Instrumentation.callActivityOnStart（Instrumentation.java:1171）上
08-07 04:48:19.271:E/AndroidRuntime（25461）：在android.app.Activity.performStart（Activity.java:5241）上
08-07 04:48:19.271:E/AndroidRuntime（25461）：在android.app.ActivityThread.performLaunchActivity（ActivityThread.java:2168）
08-07 04:48:19.271:E/AndroidRuntime（25461）：…还有11个

---

希望大家能给点建议或提供一些解决方案。非常感谢。

在您的主要活动中，更改以下内容：

if(myData.length != 0){
  ListAdapter listAdapter = new ArrayAdapter<String>(getActivity(), android.R.layout.simple_list_item_1, myData);
  setListAdapter(listAdapter);
}

---

检查

myData

的空条件，然后更新适配器

if(myData!=null && mydata.length>0){
  setListAdapter(listAdapter);
}else{
  // Some messages
}

---

谢谢，我试过了，但它不起作用：（错误保持不变。谢谢它起作用：）很抱歉我的错误，因为我是编程新手。检查是否在清单文件中添加了活动？显示清单文件尝试从

捕获打印堆栈跟踪（异常e）

在您的

DBAdapter

类中。查看是否显示任何内容。谢谢大家。问题已解决！：）

08-07 04:48:19.271: E/AndroidRuntime(25461): FATAL EXCEPTION: main
08-07 04:48:19.271: E/AndroidRuntime(25461): Process: com.example.fyp2, PID: 25461
08-07 04:48:19.271: E/AndroidRuntime(25461): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.fyp2/com.example.fyp2.LecTakeAtt}: java.lang.NullPointerException: storage == null
08-07 04:48:19.271: E/AndroidRuntime(25461):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2195)
08-07 04:48:19.271: E/AndroidRuntime(25461):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
08-07 04:48:19.271: E/AndroidRuntime(25461):    at android.app.ActivityThread.access$800(ActivityThread.java:135)
08-07 04:48:19.271: E/AndroidRuntime(25461):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
08-07 04:48:19.271: E/AndroidRuntime(25461):    at android.os.Handler.dispatchMessage(Handler.java:102)
08-07 04:48:19.271: E/AndroidRuntime(25461):    at android.os.Looper.loop(Looper.java:136)
08-07 04:48:19.271: E/AndroidRuntime(25461):    at android.app.ActivityThread.main(ActivityThread.java:5017)
08-07 04:48:19.271: E/AndroidRuntime(25461):    at java.lang.reflect.Method.invokeNative(Native Method)
08-07 04:48:19.271: E/AndroidRuntime(25461):    at java.lang.reflect.Method.invoke(Method.java:515)
08-07 04:48:19.271: E/AndroidRuntime(25461):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
08-07 04:48:19.271: E/AndroidRuntime(25461):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
08-07 04:48:19.271: E/AndroidRuntime(25461):    at dalvik.system.NativeStart.main(Native Method)
08-07 04:48:19.271: E/AndroidRuntime(25461): Caused by: java.lang.NullPointerException: storage == null
08-07 04:48:19.271: E/AndroidRuntime(25461):    at java.util.Arrays$ArrayList.<init>(Arrays.java:38)
08-07 04:48:19.271: E/AndroidRuntime(25461):    at java.util.Arrays.asList(Arrays.java:155)
08-07 04:48:19.271: E/AndroidRuntime(25461):    at android.widget.ArrayAdapter.<init>(ArrayAdapter.java:128)
08-07 04:48:19.271: E/AndroidRuntime(25461):    at com.example.fyp2.LecMonFragmentTab.onCreate(LecMonFragmentTab.java:43)
08-07 04:48:19.271: E/AndroidRuntime(25461):    at android.support.v4.app.Fragment.performCreate(Fragment.java:1763)
08-07 04:48:19.271: E/AndroidRuntime(25461):    at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:913)
08-07 04:48:19.271: E/AndroidRuntime(25461):    at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1126)
08-07 04:48:19.271: E/AndroidRuntime(25461):    at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:739)
08-07 04:48:19.271: E/AndroidRuntime(25461):    at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1489)
08-07 04:48:19.271: E/AndroidRuntime(25461):    at android.support.v4.app.FragmentActivity.onStart(FragmentActivity.java:548)
08-07 04:48:19.271: E/AndroidRuntime(25461):    at android.app.Instrumentation.callActivityOnStart(Instrumentation.java:1171)
08-07 04:48:19.271: E/AndroidRuntime(25461):    at android.app.Activity.performStart(Activity.java:5241)
08-07 04:48:19.271: E/AndroidRuntime(25461):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2168)
08-07 04:48:19.271: E/AndroidRuntime(25461):    ... 11 more

if(myData.length != 0){
  ListAdapter listAdapter = new ArrayAdapter<String>(getActivity(), android.R.layout.simple_list_item_1, myData);
  setListAdapter(listAdapter);
}

if(cursor != null){
  cursor.close();
}

if(myData!=null && mydata.length>0){
  setListAdapter(listAdapter);
}else{
  // Some messages
}