从Sqlite读取行时应用程序停止

-1

我可以在SQlite数据库中插入行，但是当我尝试从SQlite检索行时，我的应用程序停止工作。这里是代码从Sqlite读取行时应用程序停止

String model; 
    public String getDataFromDB(){ 
     SQLiteDatabase db = dbHelper.getReadableDatabase(); 

     Cursor cursor = db.query(Announcement.TABLE, new String[] {Announcement.KEY_Announcement} 
       , Announcement.KEY_Announcement, 
       null, null, null, null, null); 

     if (cursor.moveToFirst()){ 

       model = cursor.getString(cursor.getColumnIndex(Announcement.KEY_Announcement)); 

     } 

     return model; 
    }

有人可以告诉哪里是实际问题？

编辑：我从android监视器复制的文本，因此，最后我发现了异常，这是它。

00-09 03:52:12.610 335-335/com.example.anum.lmslite E/AndroidRuntime: FATAL EXCEPTION: main 
                     java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.anum.lmslite/com.example.anum.lmslite.Announcement_Activities.CS101_Announcement}: android.database.sqlite.SQLiteException: no such table: Announcement (code 1): , while compiling: SELECT * FROM Announcement 
                      at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2343) 
                      at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2395) 
                      at android.app.ActivityThread.access$600(ActivityThread.java:162) 
                      at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1364) 
                      at android.os.Handler.dispatchMessage(Handler.java:107) 
                      at android.os.Looper.loop(Looper.java:194) 
                      at android.app.ActivityThread.main(ActivityThread.java:5392) 
                      at java.lang.reflect.Method.invokeNative(Native Method) 
                      at java.lang.reflect.Method.invoke(Method.java:525) 
                      at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:838) 
                      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:605) 
                      at dalvik.system.NativeStart.main(Native Method) 
                     Caused by: android.database.sqlite.SQLiteException: no such table: Announcement (code 1): , while compiling: SELECT * FROM Announcement 
                      at android.database.sqlite.SQLiteConnection.nativePrepareStatement(Native Method) 
                      at android.database.sqlite.SQLiteConnection.acquirePreparedStatement(SQLiteConnection.java:886) 
                      at android.database.sqlite.SQLiteConnection.prepare(SQLiteConnection.java:497) 
                      at android.database.sqlite.SQLiteSession.prepare(SQLiteSession.java:588) 
                      at android.database.sqlite.SQLiteProgram.<init>(SQLiteProgram.java:58) 
                      at android.database.sqlite.SQLiteQuery.<init>(SQLiteQuery.java:37) 
                      at android.database.sqlite.SQLiteDirectCursorDriver.query(SQLiteDirectCursorDriver.java:44) 
                      at android.database.sqlite.SQLiteDatabase.rawQueryWithFactory(SQLiteDatabase.java:1314) 
                      at android.database.sqlite.SQLiteDatabase.rawQuery(SQLiteDatabase.java:1253) 
                      at com.example.anum.lmslite.StudentRepo.getDataFromDB(StudentRepo.java:91) 
                      at com.example.anum.lmslite.Announcement_Activities.CS101_Announcement.onCreate(CS101_Announcement.java:46) 
                      at android.app.Activity.performCreate(Activity.java:5122) 
                      at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1084) 
                      at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2307) 
                      at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2395)  
                      at android.app.ActivityThread.access$600(ActivityThread.java:162)  
                      at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1364)  
                      at android.os.Handler.dispatchMessage(Handler.java:107)  
                      at android.os.Looper.loop(Looper.java:194)  
                      at android.app.ActivityThread.main(ActivityThread.java:5392)  
                      at java.lang.reflect.Method.invokeNative(Native Method)  
                      at java.lang.reflect.Method.invoke(Method.java:525)  
                      at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:838)  
                      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:605)  
                      at dalvik.system.NativeStart.main(Native Method)

来源

2017-10-08 bs140200456 Aqsa Anum

您需要提供您收到的错误。检查堆栈跟踪的Android Studio监视器。 – Juan

应用程序崩溃后，您应该看到一个异常和堆栈跟踪。请只发布该部分。 – Juan

例外情况是说该表不存在。这可能是因为你没有真正创建它，或者是因为它拼写错误。 – Juan

错误说没有这样的表：公告，这意味着你没有创建与姓名通报任何表

尝试在创建表声明您数据库类就像这样。

@Override 
public void onCreate(SQLiteDatabase db) { 
    // Your code goes here to create a table Announcement 
    db.execSQL("CREATE TABLE IF NOT EXISTS Announcement (" 
     + "_id INTEGER PRIMARY KEY AUTOINCREMENT " 
     + " COLUMN_ONE TEXT, " 
     + " COLUMN_TWO TEXT)" 
    ); 
}

来源

2017-10-09 00:35:14 Jerrol

-1

我想你在查询中的第三个参数是错误的。检查这个document

来源

2017-10-08 22:43:12

所以我试过这个游标cursor = db.query（Announcement.TABLE，new String [] {Announcement.KEY_Announcement} ，Announcement.KEY_Announcement +“=？”， new String [] {}，null，null，null，空值）;但仍然出现错误，我发布了异常消息 –

如果使用？（占位符），那么第四个参数需要是替换占位符的值。在你的情况下有效的KEY_Announcement。这两个（第三和第四个参数）基本上导致WHERE子句，即WHERE KEY_Announcment = yourkeyannouncementvalue。当你通过null。 **但是**，日志表明表格通知不是数据库中的表格。必须查看'DBhelper'的代码以及实例dbHelper的设置。也许尝试添加dbHelper = new dbHelper（this）;紧接在行'SQLiteDatabase db = dbHelper.getReadableDatabase（）;'行之前。 – MikeT

从Sqlite读取行时应用程序停止

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