Android 使用ViewModel，LiveData高效、简

一、思路

ViewModel作为View监听器和View进行绑定，LiveData数据存放在ViewModel数据持久化，并具有观察性。View通过监听LiveData的数据变化，进行相应的UI操作。
UserRepository作为数据来源层，可以是本地数据库SqlLite,本地文件，网络数据

二、核心代码

• 1、ViewModel

package com.example.viewmodel_livedata.viewmodel;

import com.example.viewmodel_livedata.bean.LoginBean;
import com.example.viewmodel_livedata.repository.UserRepository;

import androidx.lifecycle.MediatorLiveData;
import androidx.lifecycle.ViewModel;

public class UserViewModel extends ViewModel {
    public MediatorLiveData<LoginBean> liveData = new MediatorLiveData<>();
    private UserRepository userRepository = new UserRepository();
    /**
     * 请求登录
     *
     * @param userName
     * @param pwd
     */
    public void requestLogin(String userName, String pwd) {
        liveData.setValue(userRepository.execueLogin(userName, pwd));
    }


}

• 2、Repository

package com.example.viewmodel_livedata.repository;

import com.example.viewmodel_livedata.bean.LoginBean;

public class UserRepository {
    /**
     * 模拟 服务器登录
     * @param userName
     * @param pwd
     * @return
     */
    public  LoginBean execueLogin(String userName, String pwd) {
        if ("123".equals(userName) && pwd.equals("456")) {
            return new LoginBean(200, " 登录成功");
        } else {
            return new LoginBean(400, " 登录失败");
        }
    }
}

• 3、View

package com.example.viewmodel_livedata;

import android.os.Bundle;
import android.view.View;
import android.widget.Toast;

import com.example.viewmodel_livedata.bean.LoginBean;
import com.example.viewmodel_livedata.viewmodel.UserViewModel;

import androidx.appcompat.app.AppCompatActivity;
import androidx.lifecycle.Observer;
import androidx.lifecycle.ViewModelProviders;


public class MainActivity extends AppCompatActivity {
    private UserViewModel viewModel;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        viewModel = ViewModelProviders.of(this).get(UserViewModel.class);
        viewModel.liveData.observe(this, new Observer<LoginBean>() {
            @Override
            public void onChanged(LoginBean loginBean) {
                Toast.makeText(MainActivity.this, loginBean.toString(), Toast.LENGTH_LONG).show();
            }
        });

    }

    public void login(View view) {
        viewModel.requestLogin("123","4567");
    }
}

三、源码传送门

https://gitee.com/daxiaa/viewmodel_livedata