使用ViewModel保存数据

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<Integer> 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);
    }
}