使用viewModel保存数据，使App被系统kill后，再次启动依然可以恢复被kill前的数据

下面的

model = ViewModelProviders.of(this,new SavedStateViewModelFactory(this)).get(MyViewModel.class);

api过时了，没有此方法了，仅记录下实现保存数据的思路

1.导入

implementation 'androidx.lifecycle:lifecycle-viewmodel-savedstate:1.0.0-alpha01'

2.定义构造函数

导入lifecycle-viewmodel-savedstate后ViewModel中可以使用带有一个参数的构造函数

private MyViewModel(SavedStateHandle handle){

this.handle = handle;

}

public MutableLiveData getNumber() {

if(!handle.contains(MainActivity.KEY_NUMBER)){

handle.set(MainActivity.KEY_NUMBER,0);

}

return handle.getLiveData(MainActivity.KEY_NUMBER);

}

//定义方法保存数据

public void add(){

getNumber().setValue(getNumber().getValue() + 1);

}

3.在Activity中的代码调整

import androidx.appcompat.app.AppCompatActivity;

import androidx.databinding.DataBindingUtil;

import androidx.lifecycle.SavedStateViewModelFactory;

import androidx.lifecycle.ViewModelProviders;

import android.os.Bundle;

import com.gao.viewmodelrestore.databinding.ActivityMainBinding;

public class MainActivity extends AppCompatActivity {

MyViewModel model;

ActivityMainBinding binding;

public static final String KEY_NUMBER = "key_number";

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);

binding = DataBindingUtil.setContentView(this, R.layout.activity_main);

// model = ViewModelProviders.of(this).get(MyViewModel.class);

//下面的api过时了，不能用了

model = ViewModelProviders.of(this,new SavedStateViewModelFactory(this)).get(MyViewModel.class);

binding.setData(model);

binding.setLifecycleOwner(this);

}

}