Android 无法启动活动组件信息{…添加团队}:java.lang.NullPointerException

我是Android编程的新手，希望有人能帮助我。我试图使用数据库表

Leagues

中的列名

Leagues\u name

填充微调器，但在尝试此操作时遇到以下错误：

Process: com.example.android.soccerleaguesapp, PID: 11770
   java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.android.soccerleaguesapp/com.example.android.soccerleaguesapp.add_team}: java.lang.NullPointerException
       at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2195)
       at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
       at android.app.ActivityThread.access$800(ActivityThread.java:135)
       at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
       at android.os.Handler.dispatchMessage(Handler.java:102)
       at android.os.Looper.loop(Looper.java:136)
       at android.app.ActivityThread.main(ActivityThread.java:5021)
       at java.lang.reflect.Method.invokeNative(Native Method)
       at java.lang.reflect.Method.invoke(Method.java:515)
       at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:827)
       at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:643)
       at dalvik.system.NativeStart.main(Native Method)
    Caused by: java.lang.NullPointerException
       at com.example.android.soccerleaguesapp.add_team.onCreate(add_team.java:55)
       at android.app.Activity.performCreate(Activity.java:5231)
       at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1090)
       at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2159)
       at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245) 
       at android.app.ActivityThread.access$800(ActivityThread.java:135) 
       at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196) 
       at android.os.Handler.dispatchMessage(Handler.java:102) 
       at android.os.Looper.loop(Looper.java:136) 
       at android.app.ActivityThread.main(ActivityThread.java:5021) 
       at java.lang.reflect.Method.invokeNative(Native Method) 
       at java.lang.reflect.Method.invoke(Method.java:515) 
       at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:827) 
       at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:643) 
       at dalvik.system.NativeStart.main(Native Method) 

添加团队类

---

如果您有任何帮助，我们将不胜感激。

请单击以下按钮替换您的代码

                if (leagues == null) {
                    leagues = new ArrayList<String>();
                }
                leagues.clear();
                Cursor cursor = myDb.getAllLeagues();
                if (cursor != null) {
                    while (cursor.moveToNext()) {
                        //Extract the data
                        String leagueName = cursor.getString(1);

                        leagues.add(leagueName);
                    }
                    league.setAdapter(adapter);
                }

if（leagues==null）{
leagues=新ArrayList（）；
}
leagues.clear（）；
Cursor=myDb.getAllLeagues（）；
如果（光标！=null）{
while（cursor.moveToNext（））{
//提取数据
String leagueName=cursor.getString（1）；
联盟。添加（联盟名称）；
}
设置适配器（适配器）；
}

post

add_team.xml

文件在此提供完美的解决方案。@Clara我没有想到这一点，并意识到我提供的引用id不正确，应该是

insert_team

，而不是

insert_team

，谢谢你为我指明了正确的方向。@mcclosa现在你解决了还是没有？

public Cursor getAllLeagues() {
 //Create SQLiteDatabase instance
 SQLiteDatabase db = this.getReadableDatabase();

 String[] columns = {
  ID,
  LEAGUE_NAME
 };

 //Return query to return cursor object
 return db.query(LEAGUES_TABLE, columns, null, null, null, null, null);
}

                if (leagues == null) {
                    leagues = new ArrayList<String>();
                }
                leagues.clear();
                Cursor cursor = myDb.getAllLeagues();
                if (cursor != null) {
                    while (cursor.moveToNext()) {
                        //Extract the data
                        String leagueName = cursor.getString(1);

                        leagues.add(leagueName);
                    }
                    league.setAdapter(adapter);
                }