如何检查是否存在的片段？ [英] How to check if the fragment exists?

问题描述

我想谈谈从活动中的片段，但我不知道，如果片段是可见的或没有。如果该片段不存在，我甚至不能做的空检查，因为它抛出由于铸造例外。

我如何检查是否存在碎片？

  PlayerFragment =（PlayerFragment）mManager.findFragmentById（R.id.bottom_container）;
playerFragment.onNotificationListener.updateUI（）;
 

解决方案

不要在第一次施展它。

 片f = mManager.findFragmentById（R.id.bottom_container）;
如果（F = NULL＆放大器;！＆安培;˚F的instanceof PlayerFragment）{
    PlayerFragment playerFragment =（PlayerFragment）F;
    playerFragment.onNotificationListener.updateUI（）;
}
 

如果不交与你收到的异常堆栈跟踪工作。

I am trying to talk to the fragment from activity, but I am not sure if the fragment is visible or no. If the fragment does not exist, I cannot even do null check as it throws exception due to the casting.

How do I check if the fragment exists?

PlayerFragment = (PlayerFragment) mManager.findFragmentById(R.id.bottom_container);
playerFragment.onNotificationListener.updateUI();

解决方案

Don't cast it at first.

Fragment f = mManager.findFragmentById(R.id.bottom_container);
if(f != null && f instanceof PlayerFragment) {
    PlayerFragment playerFragment = (PlayerFragment) f;
    playerFragment.onNotificationListener.updateUI();
}

If that doesn't work post the stacktrace with the exception you are receiving.

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