android用sqllite数据库实现诗词的增删改查功能

下面是一个简单的示例程序，演示如何在Android应用中使用SQLite数据库实现诗词的增删改查功能。

首先，在你的Android应用中创建一个SQLiteOpenHelper类，该类将用于创建和管理数据库。下面是一个示例代码，你可以根据自己的需要进行修改：

public class PoemDbHelper extends SQLiteOpenHelper {
    private static final String DATABASE_NAME = "poem.db";
    private static final int DATABASE_VERSION = 1;

    public PoemDbHelper(Context context) {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        final String SQL_CREATE_POEM_TABLE = "CREATE TABLE " +
                PoemContract.PoemEntry.TABLE_NAME + " (" +
                PoemContract.PoemEntry._ID + " INTEGER PRIMARY KEY AUTOINCREMENT, " +
                PoemContract.PoemEntry.COLUMN_TITLE + " TEXT NOT NULL, " +
                PoemContract.PoemEntry.COLUMN_AUTHOR + " TEXT NOT NULL, " +
                PoemContract.PoemEntry.COLUMN_CONTENT + " TEXT NOT NULL" +
                ");";

        db.execSQL(SQL_CREATE_POEM_TABLE);
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        db.execSQL("DROP TABLE IF EXISTS " + PoemContract.PoemEntry.TABLE_NAME);
        onCreate(db);
    }
}

接下来，我们需要创建一个PoemContract类，该类定义了数据库表的结构。下面是一个示例代码：

public class PoemContract {
    public static final class PoemEntry implements BaseColumns {
        public static final String TABLE_NAME = "poem";
        public static final String COLUMN_TITLE = "title";
        public static final String COLUMN_AUTHOR = "author";
        public static final String COLUMN_CONTENT = "content";
    }
}

在应用中，我们需要使用ContentValues对象来执行数据库操作。下面是一个示例代码，展示如何添加一首新诗：

PoemDbHelper dbHelper = new PoemDbHelper(context);
SQLiteDatabase db = dbHelper.getWritableDatabase();

ContentValues values = new ContentValues();
values.put(PoemContract.PoemEntry.COLUMN_TITLE, "静夜思");
values.put(PoemContract.PoemEntry.COLUMN_AUTHOR, "李白");
values.put(PoemContract.PoemEntry.COLUMN_CONTENT, "床前明月光，疑是地上霜。");

long newRowId = db.insert(PoemContract.PoemEntry.TABLE_NAME, null, values);

要更新一首诗，可以使用以下代码：

SQLiteDatabase db = mDbHelper.getWritableDatabase();

ContentValues values = new ContentValues();
values.put(PoemContract.PoemEntry.COLUMN_TITLE, "新标题");

String selection = PoemContract.PoemEntry._ID + " = ?";
String[] selectionArgs = { String.valueOf(poemId) };

int count = db.update(
        PoemContract.PoemEntry.TABLE_NAME,
        values,
        selection,
        selectionArgs);

要删除一首诗，可以使用以下代码：

SQLiteDatabase db = mDbHelper.getWritableDatabase();
String selection = PoemContract.PoemEntry._ID + " = ?";
String[] selectionArgs = { String.valueOf(poemId) };
int deletedRows = db.delete(PoemContract.PoemEntry.TABLE_NAME, selection, selectionArgs);

最后，要查询诗歌，可以使用以下代码：

SQLiteDatabase db = mDbHelper.getReadableDatabase();
String[] projection = {
        PoemContract.PoemEntry._ID,
        PoemContract.PoemEntry.COLUMN_TITLE,
        PoemContract.PoemEntry.COLUMN_AUTHOR,
        PoemContract.PoemEntry.COLUMN_CONTENT
};

String sortOrder = PoemContract.PoemEntry.COLUMN_TITLE + " DESC";

Cursor cursor = db.query(
        PoemContract.PoemEntry.TABLE_NAME,
        projection,
        null,
        null,
        null,
        null,
        sortOrder
);

while(cursor.moveToNext()) {
    long itemId = cursor.getLong(cursor.getColumnIndexOrThrow(PoemContract.PoemEntry._ID));
    String title = cursor.getString(cursor.getColumnIndexOrThrow(PoemContract.PoemEntry.COLUMN_TITLE));
    String author = cursor.getString(cursor.getColumnIndexOrThrow(PoemContract.PoemEntry.COLUMN_AUTHOR));
    String content = cursor.getString(cursor.getColumnIndexOrThrow(PoemContract.PoemEntry.COLUMN_CONTENT));
}

上面的代码将返回所有诗歌的标题、作者和内容。你可以根据自己的需要进行修改。