我尝试在新的导航组件中找到相关方法,但是没有发现相关内容。
目前我已经获取到了当前的目标位置:
mainHostFragment.findNavController().currentDestination
但我找不到任何关于显示碎片的参考。
我尝试在新的导航组件中找到相关方法,但是没有发现相关内容。
目前我已经获取到了当前的目标位置:
mainHostFragment.findNavController().currentDestination
但我找不到任何关于显示碎片的参考。
显示的片段引用(AndroidX):
java
public Fragment getForegroundFragment(){
Fragment navHostFragment = getSupportFragmentManager().findFragmentById(R.id.nav_host_fragment);
return navHostFragment == null ? null : navHostFragment.getChildFragmentManager().getFragments().get(0);
}
kotlin
val navHostFragment: Fragment? =
supportFragmentManager.findFragmentById(R.id.nav_host_fragment)
navHostFragment?.childFragmentManager?.fragments?.get(0)
这里的nav_host_fragment
是你的activity_main.xml
中fragment
标签的ID,带有android:name="androidx.navigation.fragment.NavHostFragment"
childFragmentManager.findFragmentById
会如何帮助呢? - Jakoss导航不提供任何机制来获取当前目标的实现(即Fragment本身)。
根据为活动创建事件回调,您应该通过以下方式之一与Fragment通信:
onAttach
方法中注册回调,将Activity转换为您提供的接口的实例ViewModel
,让您的Activity和Fragment进行通信。getPrimaryNavigationFragment()
获取前台片段,或者他们仅会在未来提供这样的机会!? - isabsent你可以像这样做:
override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?) {
super.onActivityResult(requestCode, resultCode, data)
val navHostFragment = supportFragmentManager.fragments.first() as? NavHostFragment
if(navHostFragment != null) {
val childFragments = navHostFragment.childFragmentManager.fragments
childFragments.forEach { fragment ->
fragment.onActivityResult(requestCode, resultCode, data)
}
}
}
但对于更高级的通信,在Fragment.onAttach()中注册具有回调方法的听众(Fragment -> Activity是单向通信
)以及SharedViewModel(双向
),重要的是拥有ViewModelProviders和Lifecycle owner,其作用域为getActivity()
。
as? NavHostFragment
并将 if 语句改为 if (navHostFragment is NavHostFragment)
。 - Shalbert基于其他回答
Fragment navHostFragment = getSupportFragmentManager().getPrimaryNavigationFragment();
Fragment fragment = navHostFragment.getChildFragmentManager().getFragments().get(0);
((Your Fragment Class) fragment).(public method inside the fragment)
对我很有效
使用Michal的答案,我编写了以下扩展函数进行测试:
@Suppress("UNCHECKED_CAST")
fun <F : Fragment> AppCompatActivity.getFragment(fragmentClass: Class<F>): F? {
val navHostFragment = this.supportFragmentManager.fragments.first() as NavHostFragment
navHostFragment.childFragmentManager.fragments.forEach {
if (fragmentClass.isAssignableFrom(it.javaClass)) {
return it as F
}
}
return null
}
使用方式如下:
val myFragment = activity.getFragment(MyFragment::class.java)
inline fun <reified T : Fragment> FragmentManager.findFragmentByClass(): T? = fragments.firstOrNull { it is T } as T?
。 - drdaanger您可以这样做:
@Override
public void onBackPressed() {
super.onBackPressed();
NavController navController = Navigation.findNavController(this, R.id.fragment);
int id=navController.getCurrentDestination().getId();
if(id == R.id.startGameFragment ){
selectedPosition(0);
} else if(id == R.id.gameFragment ){
selectedPosition(1);
} else if(id == R.id.endGameFragment){
selectedPosition(2);
}
}
private void selectedPosition(int pos){
for (int i = 0; i >=nav_view.getMenu().size(); i++) {
nav_view.getMenu().getItem(pos).setChecked(false);
}
nav_view.getMenu().getItem(pos).setChecked(true);
}
我使用 AndroidX 发布了完整的答案。 注意:在我的情况下,我需要检索其中一个子片段(可能不是第一个)。
在MainActivity中,您应该有类似以下内容:
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Toolbar toolbar = findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
DrawerLayout drawer = findViewById(R.id.drawer_layout);
NavigationView navigationView = findViewById(R.id.nav_view);
// Passing each menu ID as a set of Ids because each
// menu should be considered as top level destinations.
mAppBarConfiguration = new AppBarConfiguration.Builder(
R.id.mytest, R.id.nav_help)
.setDrawerLayout(drawer)
.build();
NavController navController = Navigation.findNavController(this, R.id.nav_host_fragment);
NavigationUI.setupActionBarWithNavController(this, navController, mAppBarConfiguration);
NavigationUI.setupWithNavController(navigationView, navController);
...
接下来,您需要创建一个检索良好片段的方法。
private MyTestFragment getMyTestFragment(){
MyTestFragment resultFragment = null;
Fragment navHostFragment = getSupportFragmentManager().findFragmentById(R.id.nav_host_fragment);
if(navHostFragment != null && navHostFragment.getChildFragmentManager() != null) {
List<Fragment> fragmentList = navHostFragment.getChildFragmentManager().getFragments();
for (Fragment fragment : fragmentList) {
if (fragment instanceof MyTest) {
resultFragment = (MyTest) fragment;
break;
}
}
}
return resultFragment;
}
终于你懂了。
从具有NavHostFragment的Activity中,可以使用以下代码片段来检索Active Fragment的实例。
kotlin。
val currentFragment = mNavHostFragment?.childFragmentManager?.primaryNavigationFragment()
java
Fragment navHostFragment = getSupportFragmentManager().getPrimaryNavigationFragment();
Fragment currentFragment = navHostFragment.getChildFragmentManager().getFragments().get(0);
primaryNavigationFragment
,即没有函数调用。 - undefined我认为可能会出现异常,因此您可以使用接口回调,这是一种可靠的方式,从一端到另一端进行通信,只需传递引用检查下面的代码。
Fragment A(){ interface ClickPostItemListener { fun onClicked(position: Int) }
val itemListener = object : ClickPostItemListener{ override fun onClicked(position: Int) { postBackNForth(position) } } } Fragment B(clickItem:ClickPostItemListener ){ clickItem() }
处理这个问题的最佳和正确方法是使用接口。视图模型应该用于在活动和片段之间传递数据。以下是我解决此问题的方法:
创建接口
interface NavigationInterface {
fun referenceCourseListFragment(fragment: CourseListFragment)
fun referenceCouseDetailFragment(fragment: CourseDetailInfoFragment)
}
请确保该活动实现了接口
class NotesActivity : AppCompatActivity(), NavigationInterface {}
确保为每个需要引用的片段创建lateinit var,然后
private lateinit var courseListFragment: CourseListFragment
private lateinit var courseDetailInfoFragment: CourseDetailInfoFragment
private lateinit var navigationInterface: NavigationInterface
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
//establish interface communication
activity?.let {
instantiateNavigationInterface(it)
}
// Inflate the layout for this fragment
fragmentView = inflater.inflate(R.layout.fragment_course_list, container,
false)
navigationInterface.referenceCourseListFragment(this)
return fragmentView
}
现在回到活动中,您应该能够通过接口回调实例化片段对象以进行引用
override fun referenceCourseListFragment(fragment: CourseListFragment) {
courseListFragment = fragment
}
override fun referenceCouseDetailFragment(fragment: CourseDetailInfoFragment)
{
courseDetailInfoFragment = fragment
}