从AndroidViewModel扩展时如何使用ViewModelProvider.Factory

Question

我想向我的ViewModel发送一个额外的参数，但这是从AndroidViewModel扩展的。如何将此参数添加到ViewModelFactory类？

视图模型

class ProjectViewModel(application: Application) : AndroidViewModel(application) {

    // need a param for project id...
}

ViewModelFactory

class ProjectViewModelFactory(val projectId: Int): ViewModelProvider.Factory {

    override fun <T : ViewModel?> create(modelClass: Class<T>): T {
        // need to send this...
        return ProjectViewModel(projectId) as T
    }
}

注意：我注意到在文档中它说：AndroidViewModel 子类必须具有一个接受Application作为唯一参数的构造函数。

所以我不知道做我想做的事是否可行（或很好）。

Answer 1

获取视图模型：

        viewModel = ViewModelProviders.of(this,
                new BListFactory(getActivity().getApplication(), 1))
                .get(BListViewModel.class);

工厂：

class BListFactory extends ViewModelProvider.NewInstanceFactory {

    @NonNull
    private final Application application;

    private final long id;

    public BListFactory(@NonNull Application application, long id) {
        this.application = application;
        this.id = id;
    }

    @NonNull
    @Override
    public <T extends ViewModel> T create(@NonNull Class<T> modelClass) {
        if (modelClass == BListViewModel.class) {
            return (T) new BListViewModel(application, id);
        }
        return null;
    }
}

安卓视图模型：

public class BListViewModel extends AndroidViewModel {

    private final long id;

    public BListViewModel(@NonNull Application application, final long id) {
        super(application);
        this.id = id;
    }
}