Question

我正在使用布尔值更新片段中的视图。

从片段开始工作，但是活动中有代码触发布尔值，但是直到我再次手动进入片段之前，视图都无法更新。

活动代码：

    billingClientLifecycle.purchaseUpdateEvent.observe(this, Observer {
        it?.let {
            Log.d("King", "John it 1$it")
            registerPurchases(it)
            subbed = if (it.isEmpty()) {
                Log.d("King", "inside empty")
                false
            } else {
                Log.d("King", "inside not empty")
                true
            }

        }
    })

片段代码

if (subbed){
        Log.d("King", "insideifsubbed$subbed")
        matchesBinding.homeBasicMessage.visibility = View.VISIBLE
        matchesBinding.homePaywallMessage.visibility = View.GONE
        matchesBinding.homeAccountHoldMessage.visibility = View.GONE
        matchesBinding.homeTransferMessage.visibility = View.GONE
    }else{
        matchesBinding.homeBasicMessage.visibility = View.GONE
        matchesBinding.homeAccountHoldMessage.visibility = View.GONE
        matchesBinding.homeTransferMessage.visibility = View.GONE
        matchesBinding.homePaywallMessage.visibility = View.VISIBLE

        Log.d("King", "insideelsesubbed$subbed")
    }

Answer 1

在您的Fragment中实现侦听器，以便您的Activity每次想要更新任何新信息时都可以向其发送回调。

例如，您可以创建

interface SubbedUpdateListener {
    fun onSubUpdate(subbed: Boolean)
}

并实现相关字段和设置器

var mSubbedUpdateListener: SubbedUpdateListener? = null; private get
fun setSubbedUpdateListener(subbedUpdateListener: SubbedUpdateListener){
    mSubbedUpdateListener = subbedUpdateListener
}

最后是调用代码：

billingClientLifecycle.purchaseUpdateEvent.observe(this, Observer {
    it?.let {
        Log.d("King", "John it 1$it")
        registerPurchases(it)
        subbed = if (it.isEmpty()) {
            Log.d("King", "inside empty")
            false
        } else {
            Log.d("King", "inside not empty")
            true
        }

        if(mSubbedUpdateListener != null){
            mSubbedUpdateListener.onSubUpdate(subbed)
        }
    }
})

在Activity内部，并在Fragment或onAttach方法内部创建新的onCreate时，可以使用传入的context，这应该是您的调用Activity，将其强制转换为Activity类，如果您对activity.setSubbedUpdateListener(this)使用Fragment，则调用implements SubbedUpdateListener。否则，您也可以传入SubbedUpdateListener的匿名或命名实例。在实施过程中，您可以检查：

override fun onSubUpdate(subbed: Boolean){
    if (subbed){
        Log.d("King", "insideifsubbed$subbed")
        matchesBinding.homeBasicMessage.visibility = View.VISIBLE
        matchesBinding.homePaywallMessage.visibility = View.GONE
        matchesBinding.homeAccountHoldMessage.visibility = View.GONE
        matchesBinding.homeTransferMessage.visibility = View.GONE
    }else{
        matchesBinding.homeBasicMessage.visibility = View.GONE
        matchesBinding.homeAccountHoldMessage.visibility = View.GONE
        matchesBinding.homeTransferMessage.visibility = View.GONE
        matchesBinding.homePaywallMessage.visibility = View.VISIBLE
        Log.d("King", "insideelsesubbed$subbed")
    }
}

编辑：对不起。刚刚意识到您在Kotlin上的写作，而我正在用Java编写示例。

Answer 2

这是因为片段已经创建，并且没有人观察到子变量的变化。将subbed布尔值设置为boolean类型的实时数据，然后在activity中设置值，并观察片段中的subbed值。

声明替代为

keybindings.json

活动代码：

val subbed : MutableLiveData<Boolean> = MutableLiveData()

片段代码

billingClientLifecycle.purchaseUpdateEvent.observe(this, Observer {
    it?.let {
        Log.d("King", "John it 1$it")
        registerPurchases(it)
        subbed.value = if (it.isEmpty()) {
            Log.d("King", "inside empty")
            false
        } else {
            Log.d("King", "inside not empty")
            true
        }
    }
})

如何从活动中更新片段中的视图

2 个答案:

声明替代为

活动代码：

片段代码