Android 如何使用SQLite保存数据

public final class FeedReaderContract {
    // To prevent someone from accidentally instantiating the contract class,
    // make the constructor private.
    private FeedReaderContract() {}
    /* Inner class that defines the table contents */
    public static class FeedEntry implements BaseColumns {
    	// 表名
        public static final String TABLE_NAME = "entry";
        // 列名
        public static final String COLUMN_NAME_TITLE = "title";
        // 列名
        public static final String COLUMN_NAME_SUBTITLE = "subtitle";
    }
}

// 创建数据库表
private static final String SQL_CREATE_ENTRIES =
    "CREATE TABLE " + FeedEntry.TABLE_NAME + " (" +
    FeedEntry._ID + " INTEGER PRIMARY KEY," +
    FeedEntry.COLUMN_NAME_TITLE + " TEXT," +
    FeedEntry.COLUMN_NAME_SUBTITLE + " TEXT)";
// 删除数据库表
private static final String SQL_DELETE_ENTRIES =
    "DROP TABLE IF EXISTS " + FeedEntry.TABLE_NAME;

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";
	private static final String SQL_CREATE_ENTRIES =
    	"CREATE TABLE " + FeedEntry.TABLE_NAME + " (" +
    	FeedEntry._ID + " INTEGER PRIMARY KEY," +
    	FeedEntry.COLUMN_NAME_TITLE + " TEXT," +
    	FeedEntry.COLUMN_NAME_SUBTITLE + " TEXT)";
	private static final String SQL_DELETE_ENTRIES =
		"DROP TABLE IF EXISTS " + FeedEntry.TABLE_NAME;
    public FeedReaderDbHelper(Context context) {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
    }
    public void onCreate(SQLiteDatabase db) {
    	// 创建数据库表
        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);
    }
}

FeedReaderDbHelper dbHelper = new FeedReaderDbHelper(getContext());

// Gets the data repository in write mode
SQLiteDatabase db = dbHelper.getWritableDatabase();
// Create a new map of values, where column names are the keys
ContentValues values = new ContentValues();
values.put(FeedEntry.COLUMN_NAME_TITLE, title);
values.put(FeedEntry.COLUMN_NAME_SUBTITLE, subtitle);
// Insert the new row, returning the primary key value of the new row
long newRowId = db.insert(FeedEntry.TABLE_NAME, null, values);

public long insert (String table, 
                String nullColumnHack, 
                ContentValues values)

SQLiteDatabase db = dbHelper.getReadableDatabase();
// Define a projection that specifies which columns from the database
// you will actually use after this query.
String[] projection = {
    BaseColumns._ID,
    FeedEntry.COLUMN_NAME_TITLE,
    FeedEntry.COLUMN_NAME_SUBTITLE
    };
// Filter results WHERE "title" = 'My Title'
String selection = FeedEntry.COLUMN_NAME_TITLE + " = ?";
String[] selectionArgs = { "My Title" };
// How you want the results sorted in the resulting Cursor
String sortOrder =
    FeedEntry.COLUMN_NAME_SUBTITLE + " DESC";
Cursor cursor = db.query(
    FeedEntry.TABLE_NAME,   // The table to query
    projection,             // The array of columns to return (pass null to get all)
    selection,              // The columns for the WHERE clause
    selectionArgs,          // The values for the WHERE clause
    null,                   // don't group the rows
    null,                   // don't filter by row groups
    sortOrder               // The sort order
    );

public Cursor query (String table, 	// 要查询的表名，不能为空
                String[] columns, 	// 要返回的列的列表。传递 null 将返回所有列
                String selection, 	// 声明要返回哪些行的过滤器，传递 null 将返回给定表的所有行
                String[] selectionArgs,  // 可以在选择中包含 ?，它将被选择参数中的值替换，按照它们在选择中出现的顺序
                String groupBy, 	// 分组过滤器，传递 null 将导致行不被分组
                String having, 		// 如果使用行分组，则过滤器声明游标中包含哪些行组，传递 null 将导致包含所有行组
                String orderBy)		// 对行进行排序，传递 null 将使用默认排序顺序，该顺序可能是无序的

List itemIds = new ArrayList<>();
while(cursor.moveToNext()) {
  long itemId = cursor.getLong(
      cursor.getColumnIndexOrThrow(FeedEntry._ID));
  itemIds.add(itemId);
}
cursor.close();

// Define 'where' part of query.
String selection = FeedEntry.COLUMN_NAME_TITLE + " LIKE ?";
// Specify arguments in placeholder order.
String[] selectionArgs = { "MyTitle" };
// Issue SQL statement.
int deletedRows = db.delete(FeedEntry.TABLE_NAME, selection, selectionArgs);

// return: 如果传入 whereClause，则影响的行数，否则为 0。要删除所有行并获取计数，请传递“1”作为 whereClause。
public int delete (String table, 		// 要操作的表名，不能为空
                String whereClause, 	// 删除时应用的可选 WHERE 子句。传递 null 将删除所有行。
                String[] whereArgs)		// 可以在 where 子句中包含 ?s，它将被 whereArgs 中的值替换。这些值将绑定为字符串。如果 whereClause 为 null 或不包含 ?s，则 whereArgs 可能为 null。

SQLiteDatabase db = dbHelper.getWritableDatabase();
// New value for one column
String title = "MyNewTitle";
ContentValues values = new ContentValues();
values.put(FeedEntry.COLUMN_NAME_TITLE, title);
// Which row to update, based on the title
String selection = FeedEntry.COLUMN_NAME_TITLE + " LIKE ?";
String[] selectionArgs = { "MyOldTitle" };
int count = db.update(
    FeedReaderDbHelper.FeedEntry.TABLE_NAME,
    values,
    selection,
    selectionArgs);

public int update (String table, 			// 要更新的表名，不能为null
                ContentValues values, 		// 从列名到新列值的映射。 null 是一个有效值，将被转换为 NULL。
                String whereClause, 		// 更新时应用的可选 WHERE 子句。传递 null 将更新所有行。
                String[] whereArgs)			// 可以在 where 子句中包含 ?s，它将被 whereArgs 中的值替换。这些值将绑定为字符串。如果 whereClause 为 null 或不包含 ?s，则 whereArgs 可能为 null。

@Override
protected void onDestroy() {
    dbHelper.close();
    super.onDestroy();
}

$ adb -s emulator-5554 shell
$ sqlite3 /data/data/com.example.app/databases/rssitems.db
SQLite version 3.3.12
Enter ".help" for instructions