我在进行一些数据库处理时遇到此异常。我在调用loadCouSpinnerData函数时收到此错误。我在评论db.loadCouSpinnerData之后尝试运行应用程序，然后运行完美。如果有人可以帮助我，那就太棒了！谢谢！干杯！
这是我的日志。
09-19 11:16:46.830: E/AndroidRuntime(1234): FATAL EXCEPTION: main
09-19 11:16:46.830: E/AndroidRuntime(1234): Process: com.project.attendancemanager, PID: 1234
09-19 11:16:46.830: E/AndroidRuntime(1234): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.project.attendancemanager/com.project.attendancemanager.TakeAttendance}: java.lang.NullPointerException
09-19 11:16:46.830: E/AndroidRuntime(1234): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2195)
09-19 11:16:46.830: E/AndroidRuntime(1234): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
09-19 11:16:46.830: E/AndroidRuntime(1234): at android.app.ActivityThread.access$800(ActivityThread.java:135)
09-19 11:16:46.830: E/AndroidRuntime(1234): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
09-19 11:16:46.830: E/AndroidRuntime(1234): at android.os.Handler.dispatchMessage(Handler.java:102)
09-19 11:16:46.830: E/AndroidRuntime(1234): at android.os.Looper.loop(Looper.java:136)
09-19 11:16:46.830: E/AndroidRuntime(1234): at android.app.ActivityThread.main(ActivityThread.java:5017)
09-19 11:16:46.830: E/AndroidRuntime(1234): at java.lang.reflect.Method.invokeNative(Native Method)
09-19 11:16:46.830: E/AndroidRuntime(1234): at java.lang.reflect.Method.invoke(Method.java:515)
09-19 11:16:46.830: E/AndroidRuntime(1234): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
09-19 11:16:46.830: E/AndroidRuntime(1234): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
09-19 11:16:46.830: E/AndroidRuntime(1234): at dalvik.system.NativeStart.main(Native Method)
09-19 11:16:46.830: E/AndroidRuntime(1234): Caused by: java.lang.NullPointerException
09-19 11:16:46.830: E/AndroidRuntime(1234): at com.android.internal.os.LoggingPrintStream.println(LoggingPrintStream.java:298)
09-19 11:16:46.830: E/AndroidRuntime(1234): at com.project.attendancemanager.DBHandler.getCourseData(DBHandler.java:129)
09-19 11:16:46.830: E/AndroidRuntime(1234): at com.project.attendancemanager.TakeAttendance.loadCouSpinnerData(TakeAttendance.java:59)
09-19 11:16:46.830: E/AndroidRuntime(1234): at com.project.attendancemanager.TakeAttendance.onCreate(TakeAttendance.java:38)
09-19 11:16:46.830: E/AndroidRuntime(1234): at android.app.Activity.performCreate(Activity.java:5231)
09-19 11:16:46.830: E/AndroidRuntime(1234): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
09-19 11:16:46.830: E/AndroidRuntime(1234): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2159)
09-19 11:16:46.830: E/AndroidRuntime(1234): ... 11 more
我的java课程。
package com.project.attendancemanager;
import java.util.List;
import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemSelectedListener;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.Spinner;
public class TakeAttendance extends Activity implements OnItemSelectedListener{
Button b;
Spinner courseSp, classSp, subSp, timeSp;
String selected;
//DBHandler db;
//int a;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_take_attendance);
courseSp=(Spinner)findViewById(R.id.courseSpinner);
classSp=(Spinner)findViewById(R.id.classSpinner);
subSp=(Spinner)findViewById(R.id.subSpinner);
timeSp=(Spinner)findViewById(R.id.timeSpinner);
//b=(Button)findViewById(R.id.subBT);
//db=new DBHandler(getApplicationContext());
loadCouSpinnerData();
courseSp.setOnItemSelectedListener(this);
}
//@Override
public void onItemSelected(AdapterView<?> parent, View view, int position,
long id) {
// TODO Auto-generated method stub
//selected=parent.getItemAtPosition(position).toString();
//loadClassSpinnerData(selected);
}
@Override
public void onNothingSelected(AdapterView<?> arg0) {
// TODO Auto-generated method stub
}
private void loadCouSpinnerData() {
// TODO Auto-generated method stub
DBHandler db=new DBHandler(getApplicationContext());
List<String> labels=db.getCourseData();
ArrayAdapter<String> dataAdapter= new ArrayAdapter<String>(this,android.R.layout.simple_spinner_item, labels);
dataAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
courseSp.setAdapter(dataAdapter);
}
/*private void loadClassSpinnerData(String sel) {
// TODO Auto-generated method stub
//DBHandler db=new DBHandler(getApplicationContext());
List<String> labels=db.getClassData(sel);
ArrayAdapter<String> dataAdapter= new ArrayAdapter<String>(this,android.R.layout.simple_spinner_item, labels);
dataAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
classSp.setAdapter(dataAdapter);
}*/
}
getCourseData（）函数：
public List<String> getCourseData()
{
List<String> data=new ArrayList<String>();
String query="SELECT * FROM CourseTB";
String a = null;
SQLiteDatabase db=this.getReadableDatabase();
Cursor cursor=db.rawQuery(query, null);
if(cursor.moveToFirst()){
do{
data.add(cursor.getString(1));
a=cursor.getString(1);
}while(cursor.moveToNext());
}
cursor.close();
db.close();
System.out.println(a);
return data;
}
Android Manifest：
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.project.attendancemanager"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk
android:minSdkVersion="8"
android:targetSdkVersion="19" />
<uses-permission android:name="android.permission.INTERNET"/>
<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name="com.project.attendancemanager.SplashScreen"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity
android:name="com.project.attendancemanager.Home"
android:label="@string/app_name" >
<intent-filter>
<action android:name="com.project.attendancemanager.HOME" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
</activity>
<activity
android:name="com.project.attendancemanager.TakeAttendance"
android:label="@string/app_name"
android:parentActivityName="com.project.attendancemanager.Home" >
<intent-filter>
<action android:name="com.project.attendancemanager.TAKEATTENDANCE" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
</activity>
<activity
android:name="com.project.attendancemanager.Eg"
android:label="@string/title_activity_eg"
android:parentActivityName="com.project.attendancemanager.TakeAttendance" >
<intent-filter>
<action android:name="com.project.attendancemanager.EG" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
</activity>
<activity
android:name="com.project.attendancemanager.LoginActivity"
android:label="@string/app_name" >
<intent-filter>
<action android:name="com.project.attendancemanager.LOGINACTIVITY" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
</activity>
</application>
</manifest>