Question

在我的项目中，我需要使用MainAcitivty中打开的片段进行操作。要对其进行存档，我需要使用AppBarConfiguration.Builder创建的标签片段才能使用fragmentManager.findFragmentByTag(currentlyShownTag)。我正在使用Android Studio中的模板-导航抽屉活动。在我的活动中，我有3个片段-主页，幻灯片，画廊。代码看起来像这样。

public class MainActivity extends AppCompatActivity {
private AppBarConfiguration mAppBarConfiguration;
private DrawerLayout drawer;
...
 @Override
protected void onCreate(Bundle savedInstanceState) {
...
drawer = findViewById(R.id.drawer_layout);
NavigationView navigationView = findViewById(R.id.nav_view);
mAppBarConfiguration = new AppBarConfiguration.Builder(
            R.id.nav_home, R.id.nav_gallery, R.id.nav_slideshow)
            .setDrawerLayout(drawer)
            .build();
NavController navController = Navigation.findNavController(this, R.id.nav_host_fragment);  
NavigationUI.setupActionBarWithNavController(this, navController, mAppBarConfiguration);
NavigationUI.setupWithNavController(navigationView, navController);
 }
}

我尝试在{_1}等项目的activity_main_drawer.xml中使用android:tag="fragment_home"，甚至在fragment_home.xml中也使用了android:id="@+id/nav_home"，但没有成功，因为String tag始终为空；

 List<Fragment> fragments = getSupportFragmentManager().getFragments();
  for(Fragment fragment:fragments){
       String tag =  fragment.getTag();
    }

如何查看调试器中现有的（家庭）片段

fragments = {ArrayList@12920}  size = 1
 0 = {NavHostFragment@12923} "NavHostFragment{f63acc7 #0 id=0x7f080081}"
  mDefaultNavHost = true
  mGraphId = 2131623936
  mNavController = {NavController@12983} 
  mAdded = true
  mAnimationInfo = null
  mArguments = null
  mBackStackNesting = 0
  mCalled = true
  mChildFragmentManager = {FragmentManagerImpl@12984} "FragmentManager{d436dbf in NavHostFragment{f63acc7}}"
  mChildNonConfig = null
  mContainer = null
  mContainerId = -1
  mDeferStart = false
  mDetached = false
  mFragmentId = 2131230849
  mFragmentManager = {FragmentManagerImpl@12921} "FragmentManager{d9baa1d in HostCallbacks{88a7492}}"
  mFromLayout = true
  mHasMenu = false
  mHidden = false
  mHiddenChanged = false
  mHost = {FragmentActivity$HostCallbacks@12985} 
  mInLayout = true
  mIndex = 0
  mInnerView = {FrameLayout@12986} "android.widget.FrameLayout{1e01c8c V.E...... ........ 0,0-720,1120 #7f080081 app:id/nav_host_fragment}"
  mIsCreated = true
  mIsNewlyAdded = false
  mLayoutInflater = {HwPhoneLayoutInflater@12987} 
  mLifecycleRegistry = {LifecycleRegistry@12988} 
  mMenuVisible = true
  mParentFragment = null
  mPerformedCreateView = true
  mPostponedAlpha = 0.0
  mRemoving = false
  mRestored = false
  mRetainInstance = false
  mRetaining = false
  mSavedFragmentState = null
  mSavedUserVisibleHint = null
  mSavedViewState = null
  mState = 4
  mTag = null
  mTarget = null
  mTargetIndex = -1
  mTargetRequestCode = 0
  mUserVisibleHint = true
  mView = {FrameLayout@12986} "android.widget.FrameLayout{1e01c8c V.E...... ........ 0,0-720,1120 #7f080081 app:id/nav_host_fragment}"
  mViewLifecycleOwner = {Fragment$3@12989} 
  mViewLifecycleOwnerLiveData = {MutableLiveData@12990} 
  mViewLifecycleRegistry = {LifecycleRegistry@12991} 
  mViewModelStore = null
  mWho = "android:fragment:0"
  shadow$_klass_ = {Class@12427} "class androidx.navigation.fragment.NavHostFragment"
  shadow$_monitor_ = -1889293113

导航抽屉-将标签添加到片段

0 个答案: