Question

我目前正在计算机科学A级控制的评估中，正在构建一个旨在帮助领导者管理其侦察员小组的应用程序。这是我第一次使用Android Studio，Java，sqlite或XML进行工作，因此我遇到了很多问题，这是最近的一个问题。我正在尝试创建一个函数，该函数将从表中生成随机膳食，以便为某个事件创建膳食计划。下面，我将找到的代码放在databaseHandler类中：

//Select a random lunch
public Cursor getRandomMeal()
{
    String whereClause = COLUMN_MTYPE + "=?";
    String[] whereArgs = new String[]{"Lunch"};
    String columns[] = new String[]{COLUMN_MEID + " AS " + BaseColumns._ID, COLUMN_MNAME, COLUMN_MTYPE, COLUMN_INGR, COLUMN_FCOST};
    Cursor cursor = db.query(TABLE_FOOD, columns, whereClause, whereArgs, null, null, "RANDOM()limit 1");
    return cursor;
}

紧随其后的是类的代码，该活动在其中被调用：

double TotalFoodCost;
    if (providingfood=true)
    {
        Cursor FoodItem = FoodDatabaseHandler.getRandomMeal();
        String FoodName = FoodItem.getString(FoodItem.getColumnIndex(FoodDatabaseHandler.COLUMN_MNAME));//error is apparently occurring here
        String FoodIngredients = FoodItem.getString(FoodItem.getColumnIndex(FoodDatabaseHandler.COLUMN_INGR));
        double FoodPricePerPerson = FoodItem.getDouble(FoodItem.getColumnIndex(FoodDatabaseHandler.COLUMN_FCOST));
        TotalFoodCost = FoodPricePerPerson*(31-ScoutsRemaining);//31 due to the head leader being included
        FoodDatabaseHandler.close();
    }
    else
    {
        TotalFoodCost=0;
    }

最后，这是发生错误时LogCat显示的内容：

01-25 18:27:08.785 29383-29383/com.example.atomi.scoutmanagerprototype E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.atomi.scoutmanagerprototype, PID: 29383
java.lang.IllegalStateException: Could not execute method for android:onClick
    at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:390)
    at android.view.View.performClick(View.java:4761)
    at android.view.View$PerformClick.run(View.java:19767)
    at android.os.Handler.handleCallback(Handler.java:739)
    at android.os.Handler.dispatchMessage(Handler.java:95)
    at android.os.Looper.loop(Looper.java:135)
    at android.app.ActivityThread.main(ActivityThread.java:5310)
    at java.lang.reflect.Method.invoke(Native Method)
    at java.lang.reflect.Method.invoke(Method.java:372)
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:901)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:696)
 Caused by: java.lang.reflect.InvocationTargetException
    at java.lang.reflect.Method.invoke(Native Method)
    at java.lang.reflect.Method.invoke(Method.java:372)
    at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:385)
    at android.view.View.performClick(View.java:4761) 
    at android.view.View$PerformClick.run(View.java:19767) 
    at android.os.Handler.handleCallback(Handler.java:739) 
    at android.os.Handler.dispatchMessage(Handler.java:95) 
    at android.os.Looper.loop(Looper.java:135) 
    at android.app.ActivityThread.main(ActivityThread.java:5310) 
    at java.lang.reflect.Method.invoke(Native Method) 
    at java.lang.reflect.Method.invoke(Method.java:372) 
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:901) 
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:696) 
 Caused by: android.database.CursorIndexOutOfBoundsException: Index -1 requested, with a size of 1
    at android.database.AbstractCursor.checkPosition(AbstractCursor.java:426)
    at android.database.AbstractWindowedCursor.checkPosition(AbstractWindowedCursor.java:136)
    at android.database.AbstractWindowedCursor.getString(AbstractWindowedCursor.java:50)
    at com.example.atomi.scoutmanagerprototype.frmCreateEvent2.saveAndExit(frmCreateEvent2.java:154)
    at java.lang.reflect.Method.invoke(Native Method) 
    at java.lang.reflect.Method.invoke(Method.java:372) 
    at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:385) 
    at android.view.View.performClick(View.java:4761) 
    at android.view.View$PerformClick.run(View.java:19767) 
    at android.os.Handler.handleCallback(Handler.java:739) 
    at android.os.Handler.dispatchMessage(Handler.java:95) 
    at android.os.Looper.loop(Looper.java:135) 
    at android.app.ActivityThread.main(ActivityThread.java:5310) 
    at java.lang.reflect.Method.invoke(Native Method) 
    at java.lang.reflect.Method.invoke(Method.java:372) 
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:901) 
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:696)

我很努力，因为在阅读错误消息后似乎无法解决该问题-如果有人可以指出正确的方向，那就太好了。

CursorIndexOutOfBoundsException尝试从数据库（Android Studio）导出详细信息时

0 个答案: