我在Android中玩碎片。
我知道我可以通过使用以下代码更改一个片段:
FragmentManager fragMgr = getSupportFragmentManager();
FragmentTransaction fragTrans = fragMgr.beginTransaction();
MyFragment myFragment = new MyFragment(); //my custom fragment
fragTrans.replace(android.R.id.content, myFragment);
fragTrans.addToBackStack(null);
fragTrans.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_FADE);
fragTrans.commit();
我的问题是，在Java文件中，如何获得当前显示的片段实例?
当前回答
受泰尼回答的启发，以下是我的观点。与大多数其他实现相比几乎没有修改。
private Fragment getCurrentFragment() {
FragmentManager fragmentManager = myActivity.getSupportFragmentManager();
int stackCount = fragmentManager.getBackStackEntryCount();
if( fragmentManager.getFragments() != null ) return fragmentManager.getFragments().get( stackCount > 0 ? stackCount-1 : stackCount );
else return null;
}
如果“myActivity”是您当前的活动，则将“myActivity”替换为“this”或使用对您的活动的引用。
其他回答
受泰尼回答的启发，以下是我的观点。与大多数其他实现相比几乎没有修改。
private Fragment getCurrentFragment() {
FragmentManager fragmentManager = myActivity.getSupportFragmentManager();
int stackCount = fragmentManager.getBackStackEntryCount();
if( fragmentManager.getFragments() != null ) return fragmentManager.getFragments().get( stackCount > 0 ? stackCount-1 : stackCount );
else return null;
}
如果“myActivity”是您当前的活动，则将“myActivity”替换为“this”或使用对您的活动的引用。
以上30个答案都不适合我。但这是一个有效的答案:
使用Kotlin，当使用导航组件时:
fun currentVisibleFragment(): Fragment? {
return supportFragmentManager.fragments.first()?.getChildFragmentManager()?.getFragments()?.get(0)
}
每次当你显示fragment时，你必须把它标签放入backstack:
FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
ft.setTransition(FragmentTransaction.TRANSIT_ENTER_MASK);
ft.add(R.id.primaryLayout, fragment, tag);
ft.addToBackStack(tag);
ft.commit();
然后当你需要获取当前片段时，你可以使用这个方法:
public BaseFragment getActiveFragment() {
if (getSupportFragmentManager().getBackStackEntryCount() == 0) {
return null;
}
String tag = getSupportFragmentManager().getBackStackEntryAt(getSupportFragmentManager().getBackStackEntryCount() - 1).getName();
return (BaseFragment) getSupportFragmentManager().findFragmentByTag(tag);
}
In the main activity, the onAttachFragment(Fragment fragment) method is called when a new fragment is attached to the activity. In this method, you can get the instance of the current fragment. However, the onAttachFragment(Fragment fragment) method is not called when a fragment is popped off the back stack, ie, when the back button is pressed to get the top fragment on top of the stack. I am still looking for a callback method that is triggered in the main activity when a fragment becomes visible inside the activity.
请尝试这种方法.....
private Fragment getCurrentFragment(){
FragmentManager fragmentManager = getSupportFragmentManager();
String fragmentTag = fragmentManager.getBackStackEntryAt(fragmentManager.getBackStackEntryCount() - 1).getName();
Fragment currentFragment = getSupportFragmentManager()
.findFragmentByTag(fragmentTag);
return currentFragment;
}
