android:如何检查dialogfragment是否显示 [英] android: how do I check if dialogfragment is showing

问题描述

我使用以下命令启动对话框片段

I launch my dialog fragment using

FragmentTransaction ft = 
getFragmentManager().beginTransaction();
MyDialogFragment dialog = new MyDialogFragment()
dialog.show(ft, "dialog");

然后了解一下

Fragment prev = getFragmentManager().findFragmentByTag("dialog");

但是一旦得到prev，如何检查它是否显示?

but once I get prev, how do I check if it is showing?

背景故事

我的问题是我的循环代码不断地启动对话框.但是，如果对话框已经显示，我不希望它再次启动. 这回故事只是为了背景.我寻求的答案不是:将其移出循环."

My problem is that my looping code keeps launching the dialog again and again. But if the dialog is already showing, I don't want it to launch again. This back story is just for context. The answer I seek is not: "move it out of the loop."

推荐答案

简单检查其是否为空

if(prev == null)
    //There is no active fragment with tag "dialog"
else
    //There is an active fragment with tag "dialog" and "prev" variable holds a reference to it.

或者，您可以检查片段prev当前与之关联的活动，但是，请确保在之后询问是否不为null或得到NullPointerException.像这样:

Alternatively, you could check the activity the fragment prev is currently associated with, however, make sure you ask that after you make sure it's not null or you'll get a NullPointerException. Like this:

if(prev == null)
    //There is no active fragment with tag "dialog"
else
    if(prev.getActivity() != this) //additional check
        //There is a fragment with tag "dialog", but it is not active (shown) which means it was found on device's back stack.
    else
        //There is an active fragment with tag "dialog"

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