数据库的增删改查

数据库,我们首先要创建一个类,里面用来创建表

public class BlackNumberDBOpenHelper extends SQLiteOpenHelper {

    public BlackNumberDBOpenHelper(Context context) {
        super(context, "itheima.db", null, 1);
    }

    //数据库第一次被创建时调用，适合初始化数据库里的表结构
    @Override
    public void onCreate(SQLiteDatabase db) {

        //id主键自增长  peoplename姓名  phonenumber电话号码  mode拦截模式 (1是电话  2是短信  3是电话+短信)
        db.execSQL("create table blacknumber(_id INTEGER PRIMARY KEY AUTOINCREMENT,peoplename VARCHAR(20),phonenumber VARCHAR(20),mode VARCHAR(2))");

    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

    }
}

创建好了以后我们就开始写他的增删改查了

public class BlackNumberDao {

    private BlackNumberDBOpenHelper blackNumberDBOpenHelper;

    //在构造方法里初始化helper对象
    public BlackNumberDao(Context context) {
        blackNumberDBOpenHelper = new BlackNumberDBOpenHelper(context);
    }

    //方法  添加
    public boolean add(String peoplename, String phonenumber, String mode) {
        SQLiteDatabase writableDatabase = blackNumberDBOpenHelper.getWritableDatabase();
        ContentValues contentValues = new ContentValues();
        contentValues.put("peoplename", peoplename);
        contentValues.put("phonenumber", phonenumber);
        contentValues.put("mode", mode);
        long result = writableDatabase.insert("blacknumber", null, contentValues);
        writableDatabase.close();//关闭数据库
        if (result != -1) {
            return true;
        } else {
            return false;
        }
    }

    //方法 删除
    public boolean delete(String phonenumber) {
        SQLiteDatabase writableDatabase = blackNumberDBOpenHelper.getWritableDatabase();
        int result = writableDatabase.delete("blacknumber", "phonenumber=?", new String[]{phonenumber});
        writableDatabase.close();//关闭数据库
        if (result > 0) {
            return true;
        } else {
            return false;
        }
    }

    //方法 修改拦截模式
    public boolean updateMode(String phonenumber, String newMode) {
        SQLiteDatabase writableDatabase = blackNumberDBOpenHelper.getWritableDatabase();
        ContentValues contentValues = new ContentValues();
        contentValues.put("mode", newMode);
        int result = writableDatabase.update("blacknumber", contentValues, "phonenumber=?", new String[]{phonenumber});
        writableDatabase.close();//关闭数据库
        if (result > 0) {
            return true;
        } else {
            return false;
        }
    }

    //方法 查询某个号码的拦截模式  如果返回null代表当前号码不是黑名单号码
    public String find(String phonenumber) {
        String mode = null;
        SQLiteDatabase readableDatabase = blackNumberDBOpenHelper.getReadableDatabase();
        Cursor cursor = readableDatabase.query("blacknumber", new String[]{"mode"}, "phonenumber=?", new String[]{phonenumber}, null, null, null);
        if (cursor.moveToNext()) {
            mode = cursor.getString(0);
        }
        cursor.close();
        readableDatabase.close();
        return mode;
    }

    //方法  查询黑名单里的所有信息
    public List findAll() {
        SQLiteDatabase readableDatabase = blackNumberDBOpenHelper.getReadableDatabase();
        List infos = new ArrayList<>();
        Cursor cursor = readableDatabase.query("blacknumber", new String[]{"_id", "peoplename", "phonenumber", "mode"}, null, null, null, null, null);
        while (cursor.moveToNext()) {
            String _id = cursor.getString(0);
            String peoplename = cursor.getString(1);
            String phonenumber = cursor.getString(2);
            String mode = cursor.getString(3);
            BlackNumberInfo info = new BlackNumberInfo();
            info.setId(_id);
            info.setPeoplename(peoplename);
            info.setPhonenumber(phonenumber);
            info.setMode(mode);
            infos.add(info);
        }
        cursor.close();
        readableDatabase.close();
        return infos;
    }

}

这其实可以当成一个工具类,我们用的时候就直接改表名就好了