ViewModelSHP

//繼承AndroidViewModel可以直接訪問系統資源和SharedPreferences 
public class MyViewModel extends AndroidViewModel { 
//    // 這裏也可以定義context
//    Application application;

    SavedStateHandle handle;
    String key = getApplication().getResources().getString(R.string.data_key);
    String shpname = getApplication().getResources().getString(R.string.shp_name);

    public MyViewModel(@NonNull Application application, SavedStateHandle handle) {
        super(application);
        this.handle = handle;

        if (!handle.contains(key)) {
            load();
        }
    }

    public LiveData<Integer> getNumber() {
        return handle.getLiveData(key);
    }

    public void load() {
        SharedPreferences shp = getApplication().getSharedPreferences(shpname, Context.MODE_PRIVATE);
        int x = shp.getInt(key, 0);
        handle.set(key, x);
    }

    public void save() {
        SharedPreferences shp = getApplication().getSharedPreferences(shpname, Context.MODE_PRIVATE);
        SharedPreferences.Editor editor = shp.edit();
        editor.putInt(key, getNumber().getValue());
        editor.apply();
    }

    public void add(int x) {
        handle.set(key, getNumber().getValue() == null ? 0 : getNumber().getValue() + x);
        //save();
    }

}

public class MainActivity extends AppCompatActivity {
    MyViewModel myViewModel;
    ActivityMainBinding binding;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        binding = DataBindingUtil.setContentView(this,R.layout.activity_main);
        // 如果是定義了context  這裏就獲取context
//        myViewModel.application = getApplication();
        myViewModel = new ViewModelProvider(this).get(MyViewModel.class);
        binding.setData(myViewModel);
        binding.setLifecycleOwner(this);
    }
//在onPause時保存
    @Override
    protected void onPause() {
        super.onPause();
        myViewModel.save();
    }
}