我正在关注android网站上的教程。 http://developer.android.com/training/basics/data-storage/databases.html#DefineContract
SQL_DATA_ENTRIES在FeedReaderDbHelper中以红色点亮。如何从FeedReaderDbHelper访问它?我会使用getter和setter方法还是有更好的方法?
// FeedReaderDbHelper
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
/**
* Created by Neil Armstrong on 6/5/2015.
*/
public class FeedReaderDbHelper extends SQLiteOpenHelper {
// If you change the database schema, you must increment the database version.
public static final int DATABASE_VERSION = 1;
public static final String DATABASE_NAME = "FeedReader.db";
public FeedReaderDbHelper(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
public void onCreate(SQLiteDatabase db) {
db.execSQL(SQL_CREATE_ENTRIES);
}
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// This database is only a cache for online data, so its upgrade policy is
// to simply to discard the data and start over
db.execSQL(SQL_DELETE_ENTRIES);
onCreate(db);
}
public void onDowngrade(SQLiteDatabase db, int oldVersion, int newVersion) {
onUpgrade(db, oldVersion, newVersion);
}
}
// FeedReaderContract
import android.provider.BaseColumns;
/**
* Created by Neil Armstrong on 6/5/2015.
*/
public final class FeedReaderContract {
// To prevent someone from accidentally instantiating the contract class,
// give it an empty constructor.
public FeedReaderContract() {}
/* Inner class that defines the table contents */
public static abstract class FeedEntry implements BaseColumns {
public static final String TABLE_NAME = "entry";
public static final String COLUMN_NAME_ENTRY_ID = "entryid";
public static final String COLUMN_NAME_TITLE = "title";
public static final String COLUMN_NAME_SUBTITLE = "subtitle";
private static final String TEXT_TYPE = " TEXT";
private static final String COMMA_SEP = ",";
//this is what I am trying to get.
private static final String SQL_CREATE_ENTRIES =
"CREATE TABLE " + FeedEntry.TABLE_NAME + " (" +
FeedEntry._ID + " INTEGER PRIMARY KEY," +
FeedEntry.COLUMN_NAME_ENTRY_ID + TEXT_TYPE + COMMA_SEP +
FeedEntry.COLUMN_NAME_TITLE + TEXT_TYPE + COMMA_SEP +
// Any other options for the CREATE command
" )";
private static final String SQL_DELETE_ENTRIES =
"DROP TABLE IF EXISTS " + FeedEntry.TABLE_NAME;
}
}
最佳答案
在private String SQL_CREATE_ENTRIES
类中使用FreeReaderContract
变量时,应使用getter和setter来检索/编辑它。
或者,您可以将它们打包为私有,然后使用FreeREaderContract.SQL_CREATE_ENTRIES
从FreeReaderDbHelper
类中获取,因为它们是static
变量。 (假设它们在同一包中)