Android 之SQLite（增 删 改 查）

1. 创建数据库 建表 查询语句

public class DbSqliteOpenHelper extends SQLiteOpenHelper {

private static final String TAG = "DbSqliteOpenHelper";

    //更改构造方法
    public DbSqliteOpenHelper(Context context) {
        super(context, "student.db", null, 1);
        // TODO Auto-generated constructor stub
    }
//创建数据库
    /**
     * students  表名
     * _id       标识
     * name      姓名
     * sex       年龄
     * love      爱好
     */
    @Override
    public void onCreate(SQLiteDatabase db) {

        db.execSQL("create table students(_id integer primary key, name varchar(30),sex integer,love varchar(100))");
          Log.i(TAG, "onCreate 方法执行了");
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        // TODO Auto-generated method stub

    }

}

1. 增 删 改 查的方法

public class StudentDao {
     private static final String TAG = "StudentDao";
    private DbSqliteOpenHelper helper;

     //构造方法
    public StudentDao(Context context){
        helper=new DbSqliteOpenHelper(context);
    }

    /**
     * 插入方法
     * @param name 姓名
     * @param sex 性别
     * @param love 爱好
     */

      public long insert(String name, int sex, String love) {
          // 获取数据
          SQLiteDatabase db = helper.getWritableDatabase();
          // 填充占位符
          ContentValues values = new ContentValues();
          values.put("name", name);
          values.put("sex", sex);
          values.put("love", love);
          String nullColumnHack = "values(null,?,?,?)";
          // 执行SQL
          long insert = db.insert("students", nullColumnHack, values);
          // 关闭数据库连接
          db.close();
          return insert;
   }
    /**

     * 修改更改 update
     * @param name 姓名
     * @param sex 性别
     * @param love 爱好
     */
    public int update(String name, int sex, String love) {
        // 获取数据
        SQLiteDatabase db = helper.getWritableDatabase();
        String sql = "update students set sex=?,love=? where name=?";
        // 填充占位符
        ContentValues values = new ContentValues();
        values.put("sex", sex);
        values.put("love", love);   
        // 执行SQL
        int update = db.update("students", values, " name=?", new String[]{name});
        // 关闭数据库连接
        db.close();
        return update;

 }

    /**

     * 删除

     * @param name 姓名

     */

    public int delete(String name) {
        // 获取数据
        SQLiteDatabase db = helper.getWritableDatabase();
        // 执行SQL
        int delete = db.delete("students", " name=?", new String[]{name});
        // 关闭数据库连接
        db.close();
        return delete;
 }


    /**

     * 查询全部

     *

     */

    public void getAll(){
        //获取数据
        SQLiteDatabase db = helper.getReadableDatabase();
        String sql="select _id,name,sex,like from students";
        //执行SQL
        Cursor cursor = db.rawQuery(sql, null);
        while(cursor.moveToNext()){

               int _id = cursor.getInt(cursor.getColumnIndex("_id"));

               String name = cursor.getString(cursor.getColumnIndex("name"));

               int sex = cursor.getInt(cursor.getColumnIndex("sex"));

               String like = cursor.getString(cursor.getColumnIndex("like"));
               Log.i(TAG+"======", "_id:"+_id+"name:"+name+",sex:"+sex+",like:"+like);

        }
        cursor.close();
        //关闭数据库连接
        db.close();

 }

    /**
     * 查询全部
     *  stuname   查询名字相同的所有数据
     */

    public void getOne(String stuname){
        //获取数据
        SQLiteDatabase db = helper.getReadableDatabase();
        String sql="select _id,name,sex,like from students where name=?";
         String[] selectionArgs = {stuname};
        //执行SQL
        Cursor cursor = db.rawQuery(sql, selectionArgs);
        while(cursor.moveToNext()){
               int _id = cursor.getInt(cursor.getColumnIndex("_id"));
               String name = cursor.getString(cursor.getColumnIndex("name"));
               String sex = cursor.getString(cursor.getColumnIndex("sex"));
               String like = cursor.getString(cursor.getColumnIndex("like"));
               Log.i(TAG, "_id:"+_id+"name:"+name+",sex:"+sex+",like:"+like);
        }

        cursor.close();
        //关闭数据库连接
        db.close();

 }

}

3.调用

public class MainActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        DbSqliteOpenHelper mHelper=new DbSqliteOpenHelper(this);
        //一定要调用getWritableDatabase()，
        **//才是真正的创建了数据库 又是坑啊**
        mHelper.getWritableDatabase();

        StudentDao dao=new StudentDao(this);
//      dao.insert("易皇星", 24, "喜欢运动");
//      dao.getOne("易皇星");
        dao.update("易黄星",20 , "听歌");
//      dao.delete("易皇星");
//      dao.getAll();
    }
}