java - Android Sqlite 数据库错误 - 无法创建另一个表

Question

我知道有很多关于这个问题的帖子，但我已经尝试了其中的几个，但当我调用 getHomework() 方法时，我仍然收到此错误。

Error:
android.database.sqlite.SQLiteException: no such table: homework (code 1): , while compiling: SELECT * FROM homework

DatabaseHelper - 这些是我认为错误所在的方法:

public void getHomework() {
SQLiteDatabase localSQLiteDatabase = getReadableDatabase();
String[] tblName  = {};
Cursor localCursor = localSQLiteDatabase.rawQuery("SELECT * FROM homework",tblName);

localCursor.moveToFirst();
while (localCursor.isAfterLast() == false)
{

HashMap<String, String> homework = new HashMap<String, String>();
homework.put("Subject", localCursor.getString(0));
homework.put("DueDate", localCursor.getString(1));
net.attwoodthomas.mytimetable.app.FourthActivity.mHomeworkDue.add(homework);
localCursor.moveToNext();
}


}

public void getLessons()
{
SQLiteDatabase localSQLiteDatabase = getReadableDatabase();
String[] arrayOfString = new String[2];
arrayOfString[0] = MainActivity.mWeek;
arrayOfString[1] = MainActivity.mDay;
Cursor localCursor = localSQLiteDatabase.rawQuery("SELECT Period1, Period2, Period3, Period4, Period5, Period6 FROM lessons WHERE Week = ? AND day = ?", arrayOfString);
Log.d("DatabaseHelper", "1");
localCursor.moveToNext();
Log.d("DatabaseHelper", "2");
net.attwoodthomas.mytimetable.app.SecondActivity.period1 = localCursor.getString(localCursor.getColumnIndex("Period1"));
Log.d("DatabaseHelper", "3");
net.attwoodthomas.mytimetable.app.SecondActivity.period2 = localCursor.getString(localCursor.getColumnIndex("Period2"));
Log.d("DatabaseHelper", "4");
net.attwoodthomas.mytimetable.app.SecondActivity.period3 = localCursor.getString(localCursor.getColumnIndex("Period3"));
Log.d("DatabaseHelper", "5");
net.attwoodthomas.mytimetable.app.SecondActivity.period4 = localCursor.getString(localCursor.getColumnIndex("Period4"));
Log.d("DatabaseHelper", "6");
net.attwoodthomas.mytimetable.app.SecondActivity.period5 = localCursor.getString(localCursor.getColumnIndex("Period5"));
Log.d("DatabaseHelper", "7");
net.attwoodthomas.mytimetable.app.SecondActivity.period6 = localCursor.getString(localCursor.getColumnIndex("Period6"));
Log.d("DatabaseHelper", "8");
localCursor.close();
}

public void onCreate(SQLiteDatabase paramSQLiteDatabase)
{
paramSQLiteDatabase.execSQL("CREATE TABLE lessons (Week VARCHAR(1), Day VARCHAR(10), Period1 VACHAR(20),Period2 VARCHAR(20),Period3 VARCHAR(20),Period4 VARCHAR(20),Period5 VARCHAR(20),Period6 VARCHAR(20));");
paramSQLiteDatabase.execSQL("CREATE TABLE homework (Subject VARCHAR(50), DateDue VARCHAR(50), Description VARCHAR(100));");
if (paramSQLiteDatabase.rawQuery("SELECT * FROM lessons", null).moveToFirst())
{
Log.d("DatabaseHelper", "not emtpy");
return;
}
Log.d("DatabaseHelper", "emtpy");
paramSQLiteDatabase.execSQL("INSERT INTO lessons VALUES ('A', 'Monday', 'PE', 'PE', 'SE', 'Reading', 'Drama', 'Music'), ('A', 'Tuesday', 'PE', 'PE', 'SE', 'Reading', 'Drama', 'Music'),('A', 'Wednesday', 'PE', 'PE', 'SE', 'Reading', 'Drama', 'Music'),('A', 'Thursday', 'PE', 'PE', 'SE', 'Reading', 'Drama', 'Music'),('A', 'Friday', 'PE', 'PE', 'SE', 'Reading', 'Drama', 'Music'),('B', 'Monday', 'PE', 'PE', 'SE', 'Reading', 'Drama', 'Music'),('B', 'Tuesday', 'PE', 'PE', 'SE', 'Reading', 'Drama', 'Music'),('B', 'Wednesday', 'PE', 'PE', 'SE', 'Reading', 'Drama', 'Music'), ('B', 'Thursday', 'PE', 'PE', 'SE', 'Reading', 'Drama', 'Music'),('B', 'Friday', 'PE', 'PE', 'SE', 'Reading', 'Drama', 'Music');");
paramSQLiteDatabase.execSQL("INSERT INTO homework VALUES ('Maths', '08.03.04', 'Finish p38');");
}

public void onUpgrade(SQLiteDatabase paramSQLiteDatabase, int paramInt1, int paramInt2)
{
paramSQLiteDatabase.execSQL("DROP TABLE IF EXISTS CREATE TABLE lessons (Week VARCHAR(1), Day VARCHAR(10), Period1 VACHAR(20),Period2 VARCHAR(20),Period3 VARCHAR(20),Period4 VARCHAR(20),Period5 VARCHAR(20),Period6 VARCHAR(20));");
paramSQLiteDatabase.execSQL("DROP TABLE IF EXISTS CREATE TABLE homework (Subject VARCHAR(50), DateDue VARCHAR(50), Description VARCHAR(100));");
onCreate(paramSQLiteDatabase);
}

整个项目可在 github 上获取:https://github.com/Ottermad/MyPlanner

如果我提供了太多/太少的信息，我很抱歉这是我的第一篇文章。谢谢

Answer 1

OnUpgrade 中的 DROP TABLE IF EXISTS 查询不正确。

语法是:

DROP TABLE IF EXISTS <DATABASE_NAME>.<TABLE_NAME>