android.support.v4.app.FragmentManager#findFragmentByTag ( )源码实例Demo

public static void showLanguageChooser(@NonNull FragmentManager fm) {
    FragmentTransaction ft = fm.beginTransaction();
    Fragment prev = fm.findFragmentByTag(TAG);
    if (prev != null) {
        ft.remove(prev);
    }

    ft.add(newInstance(), TAG)
            .setTransitionStyle(FragmentTransaction.TRANSIT_FRAGMENT_FADE);

    try {
        ft.commit();
    } catch (IllegalStateException e) {
        ft.commitAllowingStateLoss();
    }
}
 

/**
 * Get instance of RxSmartLockPasswordsFragment
 *
 * @return a RxSmartLockPasswordsFragment
 */
private RxSmartLockPasswordsFragment getRxFacebookAuthFragment(Builder builder) {
    FragmentManager fragmentManager = mActivity.getSupportFragmentManager();

    // prevent fragment manager already executing transaction
    int stackCount = fragmentManager.getBackStackEntryCount();
    if( fragmentManager.getFragments() != null )
        fragmentManager = fragmentManager.getFragments().get( stackCount > 0 ? stackCount-1 : stackCount ).getChildFragmentManager();

    RxSmartLockPasswordsFragment rxSmartLockPasswordsFragment = (RxSmartLockPasswordsFragment)
            fragmentManager.findFragmentByTag(RxSmartLockPasswordsFragment.TAG);

    if (rxSmartLockPasswordsFragment == null) {
        rxSmartLockPasswordsFragment = RxSmartLockPasswordsFragment.newInstance(builder);
        fragmentManager
                .beginTransaction()
                .add(rxSmartLockPasswordsFragment, RxSmartLockPasswordsFragment.TAG)
                .commit();
        fragmentManager.executePendingTransactions();
    }
    return rxSmartLockPasswordsFragment;
}
 

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
	MyLog.entry();

	final View view = inflater.inflate(R.layout.switch_listener_fragment, container, false);
	ButterKnife.inject(this, view);

	final FragmentManager fm = getFragmentManager();
	mTaskFragment = (SwitchListenerTaskFragment) fm.findFragmentByTag(TAG_TASK_FRAGMENT);
	if (mTaskFragment == null) {
		mTaskFragment = new SwitchListenerTaskFragment();
		fm.beginTransaction().add(mTaskFragment, TAG_TASK_FRAGMENT).commit();
	}
	mTaskFragment.registerCallbacks(mCallbacks);

	MyLog.exit();
	return view;
}
 

protected void initContentFragment(Bundle savedInstanceState) {
    FragmentManager fragmentManager = getSupportFragmentManager();
    if (savedInstanceState == null) {
        contentFragment = createContentFragment();
        if (contentFragment.getArguments() == null) {
            contentFragment.setArguments(getIntent().getExtras());
        }
        // SHOULD BE TRANSIT_NONE
        fragmentManager.beginTransaction()
                .setTransition(TRANSITION_INIT_FRAGMENT)
                .add(fragmentContainerId(), contentFragment, TAG_CONTENT_FRAGMENT)
                .commit();
    } else {
        //noinspection unchecked
        contentFragment = (F) fragmentManager.findFragmentByTag(TAG_CONTENT_FRAGMENT);
    }
}
 

public void displayDialog(BaseActivity activity, String tag) {
    if (activity == null || !activity.isActive()) {
        return;
    }

    FragmentManager fragmentManager = activity.getSupportFragmentManager();

    if (fragmentManager == null || fragmentManager.isDestroyed()) {
        return;
    }

    FragmentTransaction transaction = fragmentManager.beginTransaction();
    Fragment oldDialog = fragmentManager.findFragmentByTag(tag);
    if (oldDialog != null) {
        transaction.remove(oldDialog);
    }
    transaction.addToBackStack(null);

    //fix for IllegalStateException: Can not perform this action after onSaveInstanceState
    //http://stackoverflow.com/questions/15729138/on-showing-dialog-i-get-can-not-perform-this-action-after-onsaveinstancestate
    if (!activity.isActive()) { //final safeguard in case activity was closed in the middle
        return;
    }
    FragmentTransaction ft = fragmentManager.beginTransaction();
    this.show(ft, tag);
}
 

@Override
protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_earthquake_main);

  FragmentManager fm = getSupportFragmentManager();

  // Android will automatically re-add any Fragments that
  // have previously been added after a configuration change,
  // so only add it if this isn't an automatic restart.
  if (savedInstanceState == null) {
    FragmentTransaction ft = fm.beginTransaction();

    mEarthquakeListFragment = new EarthquakeListFragment();
    ft.add(R.id.main_activity_frame,
      mEarthquakeListFragment, TAG_LIST_FRAGMENT);

    ft.commitNow();
  } else {
    mEarthquakeListFragment =
      (EarthquakeListFragment) fm.findFragmentByTag(TAG_LIST_FRAGMENT);
  }

  // Retrieve the Earthquake View Model for this Activity.
  earthquakeViewModel = ViewModelProviders.of(this)
                          .get(EarthquakeViewModel.class);
}
 

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    FragmentManager fm = getSupportFragmentManager();
    BatchStepSensorFragment fragment =
            (BatchStepSensorFragment) fm.findFragmentByTag(FRAGTAG);

    if (fragment == null) {
        FragmentTransaction transaction = fm.beginTransaction();
        fragment = new BatchStepSensorFragment();
        transaction.add(fragment, FRAGTAG);
        transaction.commit();
    }

    // Use fragment as click listener for cards, but must implement correct interface
    if (!(fragment instanceof OnCardClickListener)){
        throw new ClassCastException("BatchStepSensorFragment must " +
                "implement OnCardClickListener interface.");
    }
    OnCardClickListener clickListener = (OnCardClickListener) fm.findFragmentByTag(FRAGTAG);

    mRetentionFragment = (StreamRetentionFragment) fm.findFragmentByTag(RETENTION_TAG);
    if (mRetentionFragment == null) {
        mRetentionFragment = new StreamRetentionFragment();
        fm.beginTransaction().add(mRetentionFragment, RETENTION_TAG).commit();
    } else {
        // If the retention fragment already existed, we need to pull some state.
        // pull state out
        CardStreamState state = mRetentionFragment.getCardStream();

        // dump it in CardStreamFragment.
        mCardStreamFragment =
                (CardStreamFragment) fm.findFragmentById(R.id.fragment_cardstream);
        mCardStreamFragment.restoreState(state, clickListener);
    }
}
 

public static void showOtherAppsDialog(@NonNull FragmentManager fm) {
    FragmentTransaction ft = fm.beginTransaction();
    Fragment prev = fm.findFragmentByTag(TAG);
    if (prev != null) {
        ft.remove(prev);
    }

    try {
        DialogFragment dialog = OtherAppsFragment.newInstance();
        dialog.show(ft, TAG);
    } catch (IllegalStateException | IllegalArgumentException ignored) {}
}
 

public static ConnectingDialogFragment show(FragmentManager fm) {
    try {
        Fragment fragment = fm.findFragmentByTag(TAG);
        if (fragment == null) {
            ConnectingDialogFragment dialogFragment = new ConnectingDialogFragment();
            dialogFragment.show(fm, TAG);
            return dialogFragment;
        }
        return (ConnectingDialogFragment) fragment;
    } catch (IllegalStateException e) {
        // Catch 'Cannot perform this action after onSaveInstanceState'
    }

    return null;
}
 

@NonNull
private WaitForHasClick registerKeyboardIdlingResource() {
  FragmentManager supportFragmentManager = activityTestRule.getActivity().getSupportFragmentManager();
  Fragment fragmentByTag = supportFragmentManager.findFragmentByTag(ChatActivity.CHAT_ACTIVITY_FRAGMENT);
  View viewById = fragmentByTag.getView().findViewById(R.id.attach);
  WaitForHasClick waitForHasClick = new WaitForHasClick(viewById);
  registerIdlingResources(waitForHasClick);
  return waitForHasClick;
}
 

public static void startFragment(FragmentManager fm, Fragment fragment,int resId){
    Fragment mFragment=fm.findFragmentByTag(fragment.getClass().getName());
    FragmentTransaction ft=fm.beginTransaction();
    if(mFragment==null){
        ft.add(resId,fragment,fragment.getClass().getName());
    }
    ft.show(fragment);
    ft.commitAllowingStateLoss();
}
 

@Override
public void onBackPressed() {
    FragmentManager fragmentManager = getSupportFragmentManager();
    Fragment fragment = fragmentManager.findFragmentByTag(AboutFragment.TAG);
    if (fragment == null) {
        super.onBackPressed();
    } else {
        onFragmentDetached(AboutFragment.TAG);
    }
}
 

public void show(FragmentManager fragmentManager, String tag) {
    FragmentTransaction transaction = fragmentManager.beginTransaction();
    Fragment prevFragment = fragmentManager.findFragmentByTag(tag);
    if (prevFragment != null) {
        transaction.remove(prevFragment);
    }
    transaction.addToBackStack(null);
    show(transaction, tag);
}
 

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    switch (item.getItemId()) {
        case R.id.aspect_ratio:
            FragmentManager fragmentManager = getSupportFragmentManager();
            if (mCameraView != null
                    && fragmentManager.findFragmentByTag(FRAGMENT_DIALOG) == null) {
                final Set<AspectRatio> ratios = mCameraView.getSupportedAspectRatios();
                final AspectRatio currentRatio = mCameraView.getAspectRatio();
                AspectRatioFragment.newInstance(ratios, currentRatio)
                        .show(fragmentManager, FRAGMENT_DIALOG);
            }
            return true;
        case R.id.switch_flash:
            if (mCameraView != null) {
                mCurrentFlash = (mCurrentFlash + 1) % FLASH_OPTIONS.length;
                item.setTitle(FLASH_TITLES[mCurrentFlash]);
                item.setIcon(FLASH_ICONS[mCurrentFlash]);
                mCameraView.setFlash(FLASH_OPTIONS[mCurrentFlash]);
            }
            return true;
        case R.id.switch_camera:
            if (mCameraView != null) {
                int facing = mCameraView.getFacing();
                mCameraView.setFacing(facing == CameraView.FACING_FRONT ?
                        CameraView.FACING_BACK : CameraView.FACING_FRONT);
            }
            return true;
    }
    return super.onOptionsItemSelected(item);
}
 

/**
 * Locate an existing instance of this Fragment or if not found, create and
 * add it using FragmentManager.
 *
 * @param fm The FragmentManager manager to use.
 * @return The existing instance of the Fragment or the new instance if just
 * created.
 */
public static RetainFragment findOrCreateRetainFragment(FragmentManager fm) {
    // Check to see if we have retained the worker fragment.
    RetainFragment mRetainFragment = (RetainFragment) fm.findFragmentByTag(TAG);

    // If not retained (or first time running), we need to create and add it.
    if (mRetainFragment == null) {
        mRetainFragment = new RetainFragment();
        fm.beginTransaction().add(mRetainFragment, TAG).commitAllowingStateLoss();
    }

    return mRetainFragment;
}
 

private static MediaPickHelperFragment start(FragmentManager fm, Bundle args) {
    MediaPickHelperFragment fragment = (MediaPickHelperFragment) fm.findFragmentByTag(TAG);
    if (fragment == null) {
        fragment = new MediaPickHelperFragment();
        fm.beginTransaction().add(fragment, TAG).commitAllowingStateLoss();
        fragment.setArguments(args);
    }
    return fragment;
}
 

@Override
public void show(FragmentManager manager, String tag) {
    if (manager.findFragmentByTag(tag) == null) {
        super.show(manager, tag);
    }
}
 

@Nullable public static Fragment getFragmentByTag(@NonNull FragmentManager fragmentManager, @NonNull String tag) {
    return fragmentManager.findFragmentByTag(tag);
}
 

/**
 * 查找fragment
 *
 * @param fragmentManager fragment管理器
 * @param fragmentClass   fragment类
 * @return 查找到的fragment
 */
public static Fragment findFragment(@NonNull FragmentManager fragmentManager, Class<? extends Fragment> fragmentClass) {
    List<Fragment> fragments = getFragments(fragmentManager);
    if (fragments.isEmpty())
        return null;
    return fragmentManager.findFragmentByTag(fragmentClass.getSimpleName());
}
 

/**
 * Generate by live templates.
 * Use FragmentManager to find this Fragment's instance by tag
 */
public static MainFragment findFragment(FragmentManager manager) {
    return (MainFragment) manager.findFragmentByTag(MainFragment.class.getSimpleName());
}