android MVP模式下对数据库进行简单操作

Main主页逻辑代码

public class MainActivity extends AppCompatActivity implements View.OnClickListener {    private Button btn_create,btn_add,btn_delete,btn_update,btn_query,btn_renew;    private HandlerDao hd;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        //绑定控件和添加点击事件        findView();    }    private void findView() {        btn_create= (Button) findViewById(R.id.button);        btn_add= (Button) findViewById(R.id.button2);        btn_update= (Button) findViewById(R.id.button3);        btn_query= (Button) findViewById(R.id.button4);        btn_delete= (Button) findViewById(R.id.button5);        btn_renew= (Button) findViewById(R.id.button6);        btn_create.setOnClickListener(this);        btn_add.setOnClickListener(this);        btn_update.setOnClickListener(this);        btn_query.setOnClickListener(this);        btn_delete.setOnClickListener(this);        btn_renew.setOnClickListener(this);        //调用MVP中的P也就是逻辑层代码        hd=new HandlerDaoImpl();    }    @Override    public void onClick(View v) {        String sql="";        Object [] obj=null;        switch (v.getId()){            case R.id.button:                //查看user数据库表是否存在判断是否创建成功！                sql="SELECT COUNT(*) FROM sqlite_master where type='table' and name='user'";                break;            case R.id.button2:                //插入一条测试数据                sql="insert into user(name,age) values(?,?)";                //插入的值                obj=new Object[]{"张三",20};                break;            case R.id.button3:                //根据id修改插入的数据                sql="update user set name=? where _id=?";                obj=new Object[]{"李四",1};                break;            case R.id.button4:                //查询数据库数据                sql="select * from user";                obj=null;                break;            case R.id.button5:                //根据名称删除某条数据                sql="delete from user where name=?";                obj=new Object[]{"李四"};                break;            case R.id.button6:                //更新数据库版本                sql="";                obj=null;                break;        }        //调用实现类完成具体的逻辑操作        hd.handler(v.getId(),this,sql,obj);    }}

HandDao层代码主要是一个接口

public interface HandlerDao  {    public void handler(int num, Context context, String sql, Object[] obj);}

主要的代码逻辑通过Main主页传递过来的sql语句执行相应操作

public class HandlerDaoImpl implements HandlerDao {

    //    private Context context;    //数据库表

    private UserDB userDB;    @Override    public void handler(int num, Context context, String sql,Object[] obj) {        this.context = context;        if (userDB == null) {            userDB = new UserDB(context, "user.db", null, 1);        }        switch (num) {            case R.id.button:                if (isCreate(sql)) {                    showMake("创建成功!");                } else {                    showMake("创建失败!");                }                break;            case R.id.button2:                if (isNotQuery(sql,obj)) {                    showMake("新增成功!");                } else {                    showMake("新增失败!");                }                break;            case R.id.button3:                if (isNotQuery(sql,obj)) {                    showMake("修改成功!");                } else {                    showMake("修改失败!");                }                break;            case R.id.button4:                int count = findAll(sql);                if (count > 0) {                    showMake("总共查询出" + count + "条数据!");                } else if (count == 0) {                    showMake("为查找到数据!");                } else {                    showMake("有一个未知错误!");                }                break;            case R.id.button5:                if (isNotQuery(sql,obj)) {                    showMake("删除成功!");                } else {                    showMake("删除失败!");                }                break;            case R.id.button6:                try {                    UserDB ud = new UserDB(context, "user.db", null, 2);                    SQLiteDatabase sd = userDB.getWritableDatabase();                    showMake("更新成功!");                } catch (Exception e) {                    Log.d("###", e.getMessage());                    showMake("更新失败!");                    e.printStackTrace();                }                break;        }    }    private void showMake(String message) {        Toast.makeText(context, message, Toast.LENGTH_LONG).show();    }    //创建数据库    private boolean isCreate(String sql) {        boolean isCreate = false;        try{            SQLiteDatabase sqLiteDatabase = userDB.getWritableDatabase();            Cursor cursor = sqLiteDatabase.rawQuery(sql, null);            while (cursor.moveToNext()) {                int count = cursor.getInt(0);                if (count > 0) {                    isCreate = true;                }            }            //关闭访问            sqLiteDatabase.close();        }catch (Exception e){            Log.d("###",e.getMessage());            e.printStackTrace();        }        return isCreate;    }    //新增,修改,删除数据库    private boolean isNotQuery(String sql,Object[] obj) {        SQLiteDatabase sqLiteDatabase = null;        try {            sqLiteDatabase = userDB.getWritableDatabase();            sqLiteDatabase.execSQL(sql,obj);            return true;        } catch (Exception e) {            Log.d("###", e.getMessage());            return false;        } finally {            //关闭数据库链接            sqLiteDatabase.close();        }    }    private int findAll(String sql) {        List<UserInfo> list = new ArrayList<UserInfo>();        SQLiteDatabase sqLiteDatabase=null;        try {            sqLiteDatabase = userDB.getWritableDatabase();            Cursor cursor = sqLiteDatabase.rawQuery(sql, null);            while (cursor.moveToNext()) {                UserInfo user = new UserInfo();                //根据数据库表中字段的顺序获取值                user.setId(cursor.getInt(0));                //根据数据库表中字段的名称获取值                user.setName(cursor.getColumnName(cursor.getColumnIndex("name")));                user.setAge(cursor.getInt(2));                list.add(user);            }        } catch (Exception e) {            list.clear();            Log.d("###", e.getMessage());        }        sqLiteDatabase.close();        return list.size();    }}

数据库的相应代码

public class UserDB extends SQLiteOpenHelper{    public UserDB(Context context, String name, SQLiteDatabase.CursorFactory factory, int version) {        super(context, name, factory, version);    }    public UserDB(Context context, String name, SQLiteDatabase.CursorFactory factory, int version, DatabaseErrorHandler errorHandler) {        super(context, name, factory, version, errorHandler);    }    @Override    public void onCreate(SQLiteDatabase db) {        //创建数据库表sql语句        String sql="create table user(_id integer parmary key,name varchar(10) not null,age integer not null)";        //执行创建数据库表sql        db.execSQL(sql);    }    @Override    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {        if(newVersion==2){            //开启一个事务 如果数据库表更新操作失败可以通过事务回滚            db.beginTransaction();            try{                //1:修改之前的数据库表的表名                db.execSQL("alter table user rename to user_test");                //2:创建一张新的数据库表                db.execSQL("create table user(_id integer primary key,,name varchar(20) not null,,age integer not null,see varchar(10) not null)");                //3:拷贝之前的数据库表数据到新表里面并给新添加的字段赋值                db.execSQL("insert into user select _id,name,age,'' from user_test");                //4:删除原版本数据库表                db.execSQL("drop table user_test");                //5:设置事务处理成功,如果不设置会自动回滚不会提交                db.setTransactionSuccessful();                //6：从beginTransaction开始的操作都会提交                db.endTransaction();            }catch (Exception e){                //数据库表更新操作出错因设置了事务会自动回滚                e.printStackTrace();            }        }    }}

简单的实体Bean

public class UserInfo implements Serializable{    private int id;    private String name;    private int age;    public int getAge() {        return age;    }    public void setAge(int age) {        this.age = age;    }    public int getId() {        return id;    }    public void setId(int id) {        this.id = id;    }    public String getName() {        return name;    }    public void setName(String name) {        this.name = name;    }}