详解Android中一些SQLite的增删改查操作

import android.content.ContentValues; import android.database.Cursor; import android.database.sqlite.SQLiteDatabase;  /**  * 对表的增删改查的操作。这里的表里只有uid一列作为举例。  */ public class DemoDBUtil {   //要操作的表名  public static final String DEMO_DB_NAME = "demo_db_name";  //SQLiteDatabase对象  private SQLiteDatabase sqLiteDatabase;    /**   * 带参构造方法，初始化SQLiteDatabase。   * @param sqLiteDatabase SQLiteDatabase实例   */  public DemoDBUtil(SQLiteDatabase sqLiteDatabase){   this.sqLiteDatabase = sqLiteDatabase;  }    /**   * 增加数据。   * @param uid 要新增的uid   */  public void add(String uid){   ContentValues values = new ContentValues();   values.put("uid", uid);   sqLiteDatabase.insert(DEMO_DB_NAME, null, values);  }    /**   * 删除表里所有数据。   */  public void delete(){   sqLiteDatabase.delete(DEMO_DB_NAME, null, null);  }    /**   * 删除表里与uid对应的数据。   * @param uid 某个uid   */  public void delete(String uid){   sqLiteDatabase.delete(DEMO_DB_NAME, "uid = ? ", new String[]{uid});  }    /**   * 更新表，将表所有uid替换为newUid。   */  public void update(){   ContentValues values = new ContentValues();   values.put("uid", "newUid");   sqLiteDatabase.update(DEMO_DB_NAME, values, null, null);  }    /**   * 将表里对应的uid替换为newUid。   * @param uid 表里的某个uid   */  public void update(String uid){   ContentValues values = new ContentValues();   values.put("uid", "newUid");   sqLiteDatabase.update(DEMO_DB_NAME, values, "uid = ? ", new String[]{uid});  }    /**   * 查询表里所有数据，取得uid对应的值。   */  public void query(){   Cursor cursor = sqLiteDatabase.query(DEMO_DB_NAME, null, null, null, null, null, null);   while (cursor.moveToNext()) {    String uid = cursor.getString(cursor.getColumnIndex("uid"));   }   if (null != cursor) {    cursor.close();   }  }    /**   * 取得对应uid的值。   * @param uid 表里的某个uid   */  public void query(String uid){   Cursor cursor = sqLiteDatabase.query(DEMO_DB_NAME, null, "uid = ? ", new String[]{uid}, null, null, null);   while (cursor.moveToNext()) {    String queryUid = cursor.getString(cursor.getColumnIndex("uid"));   }   if (null != cursor) {    cursor.close();   }  }    /**   * 取得最后一条记录。   */  public void queryLastRecord(){   String lastTimeSql = "select * from demo_db_name order by id desc LIMIT 1";   Cursor cursor = sqLiteDatabase.rawQuery(lastTimeSql, null);   while (cursor.moveToNext()) {    String queryUid = cursor.getString(cursor.getColumnIndex("uid"));   }   if (null != cursor) {    cursor.close();   }  } }