在TabLayout片段之间进行通信 [英] Communicating between the tablayout Fragments

问题描述

我使用带有片段的选项卡布局.情况是这样的.

I used a tab layout with fragment. The scenario goes like this.

活动:

片段1，片段2，片段3

Fragment 1 , Fragment2 , Fragment3

从Fragment2更新Fragment1的用户界面.

From Fragment2 Updating the UI of Fragment1.

我尝试从片段访问方法，但导致空指针异常.

I tried to access the methods from fragment but resulting null pointer exception.

推荐答案

1. 您可以使用Observer Pattern来实现.为此，您必须在MainActivity中创建一个MutableLiveData，并将其通过interface传递给fragment.
2. 然后从 FragmentA 发布值，并从 FragmentB 观察值，并在更改时进行操作

1. You may use Observer Pattern to achieve this. To do this, You have to create a MutableLiveData in your MainActivity and pass it to fragment through interface.
2. Then post value from FragmentA and observe it from FragmentB and do operation when change

创建界面:

interface UpdateFragmentListener {
    fun onUpdate(): MutableLiveData<Any>
}

在Activity中实现:

class MainActivity: AppCompatActivity, UpdateFragmentListener {
   val fragmentUpdate: MutableLiveData<Any> = MutableLiveData()

   ...

   override fun onUpdate(): MutableLiveData<Any> = fragmentUpdate
}

在FragmentA内部:

Inside FragmentA:

...

val updateListener: UpdateFragmentListener 

override fun onAttach(context: Context) {
    updateListener = context as UpdateFragmentListener 
}

override fun onViewCreated(v: View, savedInstanceState: Bundle) { 
    super.onViewCreated(v, savedInstanceState

    //use like this by modifying it wherever you need inside FragmentA
    updateListener.onUpdate().postValue(Any())

}

在FragmentB内部:

Inside FragmentB:

...

val updateListener: UpdateFragmentListener 

override fun onAttach(context: Context) {
    updateListener = context as UpdateFragmentListener 
}

override fun onViewCreated(v: View, savedInstanceState: Bundle) { 
    super.onViewCreated(v, savedInstanceState

    //Observe it and do operation wherever you need inside FragmentB
    updateListener.onUpdate().observe(this, Observer { 
        // implement your logic here
    })

}

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