java.lang.NullPointerException: println 需要一条消息 [英] java.lang.NullPointerException: println needs a message

问题描述

我得到错误:java.lang.NullPointerException:当我调用这个方法时，println需要一条消息:

I get the errror: java.lang.NullPointerException: println needs a message when I call this method:

lst_info = new HashMap<String, String>();
SystemDatabaseHandler db = new SystemDatabaseHandler(getApplicationContext());
lst_info = db.getLstInfo(sql_id);

系统数据库处理器:

public HashMap<String , String> getLstInfo(int id){
    HashMap<String , String> lst_temp;
    lst_temp = new HashMap<String , String>();

    String selectQuery = "SELECT * FROM dkr_lst_lst WHERE lst_id = " + id;
    SQLiteDatabase db = this.getWritableDatabase();
    Cursor cursor = db.rawQuery(selectQuery, null);
    if (cursor.moveToFirst()) {
        do {
            Log.d("sql_id", cursor.getString(0));
            lst_temp.put("sql_id", cursor.getString(0));
        }while (cursor.moveToNext());
    } 
    cursor.close();
    db.close();
    return lst_temp;
}

Log.d("sql_id", cursor.getString(0));返回:

Log.d("sql_id", cursor.getString(0)); returns:

07-12 11:56:05.603: D/sql_id(13783): 1

07-12 11:56:05.603: D/sql_id(13783): 1

原木猫:

07-12 11:56:05.613: D/Database(13783): dbclose(): path = /data/data/de.bodprod.dkr/databases/dkr, handle = 0x4301a8
07-12 11:56:05.613: D/AndroidRuntime(13783): Shutting down VM
07-12 11:56:05.613: W/dalvikvm(13783): threadid=1: thread exiting with uncaught exception (group=0x4001d5a0)
07-12 11:56:05.623: E/AndroidRuntime(13783): FATAL EXCEPTION: main
07-12 11:56:05.623: E/AndroidRuntime(13783): java.lang.RuntimeException: Unable to start activity ComponentInfo{de.bodprod.dkr/de.bodprod.dkr.BosLstDetailMap}: java.lang.NullPointerException: println needs a message
07-12 11:56:05.623: E/AndroidRuntime(13783):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1872)
07-12 11:56:05.623: E/AndroidRuntime(13783):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1893)
07-12 11:56:05.623: E/AndroidRuntime(13783):    at android.app.ActivityThread.access$1500(ActivityThread.java:135)
07-12 11:56:05.623: E/AndroidRuntime(13783):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1054)
07-12 11:56:05.623: E/AndroidRuntime(13783):    at android.os.Handler.dispatchMessage(Handler.java:99)
07-12 11:56:05.623: E/AndroidRuntime(13783):    at android.os.Looper.loop(Looper.java:150)
07-12 11:56:05.623: E/AndroidRuntime(13783):    at android.app.ActivityThread.main(ActivityThread.java:4385)
07-12 11:56:05.623: E/AndroidRuntime(13783):    at java.lang.reflect.Method.invokeNative(Native Method)
07-12 11:56:05.623: E/AndroidRuntime(13783):    at java.lang.reflect.Method.invoke(Method.java:507)
07-12 11:56:05.623: E/AndroidRuntime(13783):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:849)
07-12 11:56:05.623: E/AndroidRuntime(13783):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:607)
07-12 11:56:05.623: E/AndroidRuntime(13783):    at dalvik.system.NativeStart.main(Native Method)
07-12 11:56:05.623: E/AndroidRuntime(13783): Caused by: java.lang.NullPointerException: println needs a message
07-12 11:56:05.623: E/AndroidRuntime(13783):    at android.util.Log.println_native(Native Method)
07-12 11:56:05.623: E/AndroidRuntime(13783):    at android.util.Log.d(Log.java:137)
07-12 11:56:05.623: E/AndroidRuntime(13783):    at de.bodprod.dkr.BosLstDetailMap.onCreate(BosLstDetailMap.java:43)
07-12 11:56:05.623: E/AndroidRuntime(13783):    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1072)
07-12 11:56:05.623: E/AndroidRuntime(13783):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1836)
07-12 11:56:05.623: E/AndroidRuntime(13783):    ... 11 more
07-12 11:56:07.495: D/Process(13783): killProcess, pid=13783

推荐答案

也许当你打电话时

Log.d("sql_id", cursor.getString(0)); 

cursor.getString(0) 返回 null，然后崩溃.

cursor.getString(0) returns null, and then it crashes.

试试:

if(cursor.getString(0) != null) {
    Log.d("sql_id", cursor.getString(0)); 
}

否则，向我们展示:de.bodprod.dkr.BosLstDetailMap.onCreate(BosLstDetailMap.java:43)

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