“在android.database.sqlite.SQLitepenhelper中没有可用的默认构造函数”在Android Studio中 [英] "There is no default constructor available in android.database.sqlite.SQLitepenhelper" in Android Studio

问题描述

尝试使用SQLiteOpenHelper扩展类，但是此错误显示：没有默认构造函数可用在android.database.sqlite.SQLitepenhelper以及其他无法解析符号类别，注意...

Trying to extend class with SQLiteOpenHelper, but this error shows up : "There is no default constructor available in android.database.sqlite.SQLitepenhelper" along with other "cannot resolve symbol Category, Note,..."

class DbHelper extends SQLiteOpenHelper {


    @Override
    public void onCreate(SQLiteDatabase db) {

        db.execSQL(Category.getSql());
        db.execSQL(Note.getSql());
        db.execSQL(Attachment.getSql());
        db.execSQL(CheckItem.getSql());
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        db.execSQL("DROP TABLE IF EXISTS " + Category.TABLE_NAME);
       db.execSQL("DROP TABLE IF EXISTS " + Note.TABLE_NAME);
        db.execSQL("DROP TABLE IF EXISTS " + Attachment.TABLE_NAME);
        db.execSQL("DROP TABLE IF EXISTS " + CheckItem.TABLE_NAME);

        onCreate(db);
    }

推荐答案

自己调用 super 构造函数SQLiteOpenHelper.html> SQLiteOpenHelper 。

You need to define an explicit constructor yourself that calls the 4- or 5-arg super constructor in SQLiteOpenHelper.

例如：

public DbHelper(Context context) {
    super(context, "database.db", null, 1);
}

其中 database.db 是您的数据库文件名， 1 是版本。

where database.db is your database file name and 1 is the version.

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