如何检查在ViewModel中授予的权限? [英] How to check permission is granted in ViewModel?

问题描述

我需要询问联系人的权限，当应用程序启动时，我要问，在ViewModel部分，我需要调用需要权限的方法.我需要检查权限是否由用户授予，然后再调用，但是要检查权限，我需要具有访问活动.而在我的ViewModel中，我没有对Activity的引用，也不想拥有我该如何克服这个问题?

I need to ask permission for contacts and when application starts I'm asking,in ViewModel part I need to call method which requires permission. I need to check permission is granted by user or not and then call, but for checking permission I need to have access Activity. while in my ViewModel I don't have a reference to Activity and don't want to have, How I can overcome, the problem?

推荐答案

我只是遇到了这个问题，所以我决定改用LiveData.

I just ran into this problem, and I decided to use make use of LiveData instead.

核心概念:

• ViewModel上有一个LiveData，它需要进行哪些权限请求

• ViewModel has a LiveData on what permission request needs to be made

ViewModel有一个方法(本质上是回调)，该方法返回是否授予权限

ViewModel has a method (essentially callback) that returns if permission is granted or not

SomeViewModel.kt:

class SomeViewModel : ViewModel() {
    val permissionRequest = MutableLiveData<String>()

    fun onPermissionResult(permission: String, granted: Boolean) {
        TODO("whatever you need to do")
    }
}

FragmentOrActivity.kt

class FragmentOrActivity : FragmentOrActivity() {
    private viewModel: SomeViewModel by lazy {
        ViewModelProviders.of(this).get(SomeViewModel::class.java)
    }

    override fun onCreate(savedInstanceState: Bundle?) {
        ......
        viewModel.permissionRequest.observe(this, Observer { permission -> 
            TODO("ask for permission, and then call viewModel.onPermissionResult aftwewards")
        })
        ......
    }
}

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