安卓开发操作数据库

安卓的数据库为SQLite，使用的sql语句都是互通的，这里就不多讲了，看代码：

static ArrayAdapter adapter;
    ImageView img;
    Button add;
    Button delete;
    Button updata;
    Button select;
    ListView liv;
    SQLiteDatabase db;
    ArrayList<User> users = new ArrayList<>();
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_day06);
//        img = findViewById(R.id.img);
//        new MyAsyncTask().execute("http://upload.jianshu.io/users/upload_avatars/6416344/5e103cde-c77d-49f9-8a47-2ed4418c564a.jpg");

        add = findViewById(R.id.add);
        delete = findViewById(R.id.delete);
        updata = findViewById(R.id.updata);
        select = findViewById(R.id.select);
        liv = findViewById(R.id.liv);
        //先创建数据库对象
        MyDataBase base = new MyDataBase(this);
        db = base.getWritableDatabase();
        //增加
        add.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                getAdd();
                users.clear();
                getSelect();
            }
        });
        //删除
        delete.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                getDelete();
                users.clear();
                getSelect();
            }
        });
        //修改
        updata.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                getUpData();
                users.clear();
                getSelect();
            }
        });
        //查询
        select.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                users.clear();
                getSelect();
            }
        });
    }

定义的数据库类，继承了SQLiteOpenHelper

public class MyDataBase extends SQLiteOpenHelper {
    public MyDataBase(Context context) {
        super(context, "mydb", null, 1);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        //新建 只执行一次
        db.execSQL("create table jiao (_id integer primary key autoincrement,name varchar(10),age integer)");
        db.execSQL("insert into jiao values(null,'焦子晗',20)");
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        //更新版本号
    }
}

将各种操作的sql语句封装到各个方法中去

/**
     * 增加数据方法
     */
    public void getAdd(){
//        db.execSQL("insert into jiao values(null,'焦子澳',20)");
        ContentValues values = new ContentValues();
        values.put("name","焦子澳");
        values.put("age",20);
        db.insert("jiao",null,values);
    }
    /**
     * 删除方法
     */
    public  void getDelete(){
//        db.execSQL("delete from jiao where name = '焦子晗'");
        db.delete("jiao","name = ?",new String[]{"焦子晗"});
    }
    /**
     * 修改方法
     */
    public void getUpData(){
//        db.execSQL("update jiao set name = '焦雪' where name = ?",new String[]{"焦子澳"});
        ContentValues values = new ContentValues();
        values.put("name","焦雪");
        db.update("jiao",values,"name = ?",new String[]{"焦子澳"});
    }
    /**
     * 查询方法
     */
    public void getSelect(){
//        Cursor cursor = db.rawQuery("select * from jiao", null);
//        while(cursor.moveToNext()){
//            String name = cursor.getString(cursor.getColumnIndex("name"));
//            int age = cursor.getInt(cursor.getColumnIndex("age"));
//            int id = cursor.getInt(cursor.getColumnIndex("_id"));
//            users.add(new User(name,age,id));
//        }
        Cursor cursor = db.query("jiao", null, null, null, null, null, null);
        while(cursor.moveToNext()){
            String name = cursor.getString(cursor.getColumnIndex("name"));
            int age = cursor.getInt(cursor.getColumnIndex("age"));
            int id = cursor.getInt(cursor.getColumnIndex("_id"));
            users.add(new User(name,age,id));
        }
        adapter = new ArrayAdapter(Activity_day06.this,R.layout.support_simple_spinner_dropdown_item,users);
        liv.setAdapter(adapter);
    }

增删改查各两种方法，两种方法皆可以使用，第二种方法各有不同的参数，根据自己的情况而定；

如果想添加到ListView中去，创建集合，将数据放入集合中。

存储适配器集合数据的类

public class User{
        String name;
        int age;
        int id;

        public User(String name, int age, int id) {
            this.name = name;
            this.age = age;
            this.id = id;
        }

        @Override
        public String toString() {
            return "User{" +
                    "name='" + name + '\'' +
                    ", age=" + age +
                    ", id=" + id +
                    '}';
        }
    }