Question

将临时值插入表格中的所有列时，它似乎正常工作。请参阅以下方法并在下面记录。但是，当我测试列是否存在下面的测试方法时，它会返回false，表示该列存在!!

另外你可以在日志中看到getType为除了name列之外的列返回0 ?? !!出于这个原因，我在底部添加了表创建方法（是的，我更新了版本号）

请注意，此问题已根据以下评论进行了编辑（因此前几条评论可能没有意义）。

第一段代码来自下面两种方法的名称

ContentValues values = setContVal_All_Columns(myTable);

//create row
long insertId = database.insert(myTable, null, values);
System.out.println("Column date exists = " + String.valueOf(doesColumnExist(myTable,"date")));

setContVal_All_Columns方法：

//sets generic content values to initialize row = excluding ID column
private ContentValues setContVal_All_Columns(String myTable) {

    ContentValues contentValues = new ContentValues();
    Cursor cursor = database.query(myTable,null,null,null,null,null,null);
    String[] columnNames = cursor.getColumnNames();
    cursor.moveToFirst();

    for(String name : columnNames) {
        if(!name.equals(IdColumn)) {  //excludes Id column
            int index = cursor.getColumnIndex(name);
            System.out.println("Column name = " + name + " index = " + String.valueOf(index));
            System.out.println("Type = " + String.valueOf(cursor.getType(index))); //appears to crash on the getType
            if (cursor.getType(index) == 3) {  //String
                System.out.println("Column is string");
                contentValues.put(name, " ");
            } else if (cursor.getType(index) == 1) {  //integer
                contentValues.put(name, 0);
            }
        }
    }

    return contentValues;
}

日志信息：

02-16 19:58:42.296    9711-9711/com.mycompany.dudesmyreminders I/System.out﹕ Column name = date index = 1
02-16 19:58:42.296    9711-9711/com.mycompany.dudesmyreminders I/System.out﹕ Type = 0
02-16 19:58:42.296    9711-9711/com.mycompany.dudesmyreminders I/System.out﹕ Column name = name index = 2
02-16 19:58:42.296    9711-9711/com.mycompany.dudesmyreminders I/System.out﹕ Type = 3
02-16 19:58:42.296    9711-9711/com.mycompany.dudesmyreminders I/System.out﹕ Column is string
02-16 19:58:42.296    9711-9711/com.mycompany.dudesmyreminders I/System.out﹕ Column name = altitude index = 3
02-16 19:58:42.296    9711-9711/com.mycompany.dudesmyreminders I/System.out﹕ Type = 0
02-16 19:58:42.296    9711-9711/com.mycompany.dudesmyreminders I/System.out﹕ Column name = is_used index = 4
02-16 19:58:42.296    9711-9711/com.mycompany.dudesmyreminders I/System.out﹕ Type = 0
02-16 19:58:42.296    9711-9711/com.mycompany.dudesmyreminders I/System.out﹕ Column name = warning index = 5
02-16 19:58:42.296    9711-9711/com.mycompany.dudesmyreminders I/System.out﹕ Type = 0
02-16 19:58:42.296    9711-9711/com.mycompany.dudesmyreminders I/System.out﹕ Column name = action index = 6
02-16 19:58:42.296    9711-9711/com.mycompany.dudesmyreminders I/System.out﹕ Type = 0
02-16 19:58:42.316    9711-9711/com.mycompany.dudesmyreminders I/System.out﹕ Column date exists = false

编辑：测试栏目列表的方法：总是在日期栏上返回-1 ...

private boolean doesColumnExist(String myTable, String myColumn) {
    boolean doesExist = true;

Cursor cursor = database.rawQuery("PRAGMA table_info(" + myTable + ")",null);
cursor.moveToFirst();

int value = cursor.getColumnIndex(myColumn);

if(value == -1)
{
    doesExist = false;
}
return doesExist;
}

编辑：表格创建方法：

//Database creation sql statement
private static final String SQL_CREATE_SPECIAL_DAYS =
        "CREATE TABLE " + dbFields.TABLE_NAME_SPECIAL_DAYS + " (" +
                dbFields.COLUMN_SPECIAL_DAYS_ID + INTEGER_PRIMARY_KEY + COMMA_SEP +
                dbFields.COLUMN_SPECIAL_DAYS_DATE + TEXT_TYPE + COMMA_SEP +
                dbFields.COLUMN_SPECIAL_DAYS_NAME + TEXT_TYPE + COMMA_SEP +
                dbFields.COLUMN_SPECIAL_DAYS_ALTITUDE + INTEGER_TYPE + COMMA_SEP +
                dbFields.COLUMN_SPECIAL_DAYS_USED + INTEGER_TYPE + COMMA_SEP +
                dbFields.COLUMN_SPECIAL_DAYS_WARNING + INTEGER_TYPE + COMMA_SEP +
                dbFields.COLUMN_SPECIAL_DAYS_ACTION + INTEGER_TYPE +
                // Any other options for the CREATE command
                " )";



@Override
public void onCreate(SQLiteDatabase database) {
    database.execSQL(SQL_CREATE_SPECIAL_DAYS);
}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    Log.w(MySQLiteHelper.class.getName(),
            "Upgrading database from version " + oldVersion + " to "
                    + newVersion + ", which will destroy all old data");
    db.execSQL("DROP TABLE IF EXISTS " + dbFields.TABLE_NAME_SPECIAL_DAYS);
    onCreate(db);
}

Answer 1

查看原始代码块中的代码...

Cursor cursor = database.query(myTable,null,null,null,null,null,null);
String[] columnNames = cursor.getColumnNames();

...执行任何游标查询时，游标'index'（即它指向的数据集行）始终为-1。这是之前第一行的索引为0（有原因）。但是，此时调用getColumNames()是合法的，因为列名在查询过程中会被单独编目，并且在游标的生命周期内保持不变。

但是，调用getType()确实需要光标“指向”（引用）数据集中的有效行。文档并不完全清楚，但推断这是一个要求......

public abstract int getType（int columnIndex）在API级别11中添加

返回给定列值的数据类型。 返回列的首选类型，但数据可能会转换为get类型方法中记录的其他类型，如getInt（int），getFloat（int）等。

换句话说，除非光标引用数据集的有效行，否则无法获得首选类型。只需将光标移动到第一行（假设它在数据集中有有效的数据行），就可以获得每列中实际数据的首选类型。

所以基本上只需在使用moveToFirst() ...
之前添加getType()
Cursor cursor = database.query(myTable,null,null,null,null,null,null); String[] columnNames = cursor.getColumnNames(); if (cursor.getCount() > 0) cursor.moveToFirst(); // Calls to cursor.getType() will work from now on

Android SQLite游标getType似乎是崩溃的应用程序

1 个答案: