当 fragment 成为 backstack 的顶部时与它通信？

Question

我有两个片段：FragmentA 和 FragmentB。我从我的 ActivityMain 开始 FragmentA，然后我开始 FragmentB 而不从后台弹出 FragmentA（我想在 [=11] 的背景中显示 FragmentA =]).最终我完成了 FragmentB 并将其从后台弹出，但我需要通知片段 A FragmentB 不再使用。

如何与 FragmentA 沟通 FragmentB 已关闭并且 FragmentA 现在位于后台堆栈的顶部？

我试过在许多 Fragment 的类中放置断点，例如 OnResume()、OnAttach、OnStart()，但没有任何结果。

Answer 1

你应该使用 setTargetFragment 方法。

Optional target for this fragment. This may be used, for example, if this fragment is being started by another, and when done wants to give a result back to the first. The target set here is retained across instances via.

回到你的案例，当从 FragmentA 开始 FragmentB 时。

class FragmentA : Fragment() {

    companion object {
        val REQUEST_CODE_FRAGMENT_A = 1
    }

    override fun onCreateView(inflater: LayoutInflater?, container: ViewGroup?, savedInstanceState: Bundle?): View {
        val view = inflater?.inflate(R.layout.fragment_a, container, false)!!

        val fragmentB = FragmentB().apply {
            setTargetFragment(this@FragmentA, REQUEST_CODE_FRAGMENT_A)
        }
        fragmentManager.beginTransaction()
                .add(R.id.container, fragmentB, "fragB")
                .addToBackStack(null)
                .commit()

        return view
    }

    override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?) {
        super.onActivityResult(requestCode, resultCode, data)
        if (requestCode == REQUEST_CODE_FRAGMENT_A) {
            if (resultCode == Activity.RESULT_OK) {
                val message = data?.getStringExtra("message")
                Toast.makeText(activity, message, Toast.LENGTH_SHORT).show()
            }
        }
    }
}

当FragmentB从后台弹出时，onDestroy方法将被调用。

class FragmentB : Fragment() {

    override fun onDestroy() {
        // Notify for FragmentA (as target fragment) that FragmentB destroyed.
        val intent = Intent().apply { putExtra("message", "I'm out.") }
        targetFragment.onActivityResult(targetRequestCode, Activity.RESULT_OK, intent)
        super.onDestroy()
    }
}

当 fragment 成为 backstack 的顶部时与它通信？

Communicating with fragment when it becomes the top of the backstack?

android

android-fragments

fragmentmanager