如何通过背压完美地处理底部导航
问题描述 投票：17回答：15
我正在使用底部导航栏，但我没有得到完美的底部导航栏。
我的MainActivity课程：
public class MainActivity extends AppCompatActivity {
private static final String SELECTED_ITEM = "selected_item";
private BottomNavigationView bottomNavigationView;
private Toolbar toolbar;
private MenuItem menuItemSelected;
private int mMenuItemSelected;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
bottomNavigationView = (BottomNavigationView) findViewById(R.id.bottom_navigation);
bottomNavigationView.setOnNavigationItemSelectedListener(new BottomNavigationView.OnNavigationItemSelectedListener() {
@Override
public boolean onNavigationItemSelected(@NonNull MenuItem item) {
selectFragment(item);
return true;
}
});
//Always load first fragment as default
FragmentTransaction fragmentTransaction = getSupportFragmentManager().beginTransaction();
fragmentTransaction.replace(R.id.frameLayout, new AnnouncementFragment());
fragmentTransaction.commit();
if (savedInstanceState != null) {
mMenuItemSelected = savedInstanceState.getInt(SELECTED_ITEM, 0);
menuItemSelected = bottomNavigationView.getMenu().findItem(mMenuItemSelected);
} else {
menuItemSelected = bottomNavigationView.getMenu().getItem(0);
}
selectFragment(menuItemSelected);
}
private void selectFragment(MenuItem item) {
Fragment fragment = null;
Class fragmentClass;
switch (item.getItemId()) {
case R.id.action_announcement:
fragmentClass = AnnouncementFragment.class;
break;
case R.id.action_menu:
fragmentClass = MenuFragment.class;
break;
case R.id.action_menu_reports:
fragmentClass = ReportFragment.class;
break;
case R.id.action_setting:
fragmentClass = SettingFragment.class;
break;
default:
fragmentClass = AnnouncementFragment.class;
}
try {
fragment = (Fragment) fragmentClass.newInstance();
} catch (Exception e) {
e.printStackTrace();
}
FragmentManager fragmentManager = getSupportFragmentManager();
fragmentManager.beginTransaction().replace(R.id.frameLayout, fragment).commit();
}
@Override
protected void onSaveInstanceState(Bundle outState) {
outState.putInt(SELECTED_ITEM, mMenuItemSelected);
super.onSaveInstanceState(outState);
}
我的背部压力也不正常：
@Override
public void onBackPressed() {
MenuItem homeItem = bottomNavigationView.getMenu().getItem(0);
if (mMenuItemSelected != homeItem.getItemId()) {
selectFragment(homeItem);
} else {
super.onBackPressed();
}
}
我应该怎么做，因为底部菜单栏上的分布不均匀。如何正确维护菜单空间而不分布不均匀。
在这里，我附上了我在AVD 
15个回答
16
投票
投票
根据Material Design指南
在Android上，“后退”按钮不会在底部导航栏视图之间导航。
编辑：材料设计链接不再提及后退按钮行为。
按后退按钮可以退出应用程序，这是默认行为，例如在Google Photo中...
FragmentManager fragmentManager = getFragmentManager();
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
fragmentTransaction.replace(R.id.content, fragment);
// note: there is NOT a addToBackStack call
fragmentTransaction.commit();
......或者将用户带到家庭区域，如果再次按下，则在出口处。
就个人而言，我发现这最后的模式要好得多。
要在没有覆盖onBackPressed的情况下获取它，您需要识别主片段并将其与所有其他片段区分开来
navigation = (BottomNavigationView) findViewById(R.id.navigation);
navigation.setOnNavigationItemSelectedListener(new BottomNavigationView.OnNavigationItemSelectedListener() {
@Override
public boolean onNavigationItemSelected(@NonNull MenuItem item) {
switch (item.getItemId()) {
case R.id.navigation_home:
viewFragment(new HomeFragment(), FRAGMENT_HOME);
return true;
case R.id.navigation_page_1:
viewFragment(new OneFragment(), FRAGMENT_OTHER);
return true;
case R.id.navigation_page_2:
viewFragment(new TwoFragment(), FRAGMENT_OTHER);
return true;
}
return false;
}
});
你现在要做的是写viewfragment方法，必须：
- 知道在
commit之前堆栈中有多少片段 - 如果片段不是“home type”，请在
commit之前将其保存到堆栈中 - 添加一个
OnBackStackChangedListener，当堆栈减少时（即当我按下时），删除所有不是“home type”（POP_BACK_STACK_INCLUSIVE）的片段，将我们带到home片段
下面带有注释的完整方法
private void viewFragment(Fragment fragment, String name){
final FragmentManager fragmentManager = getFragmentManager();
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
fragmentTransaction.replace(R.id.content, fragment);
// 1. Know how many fragments there are in the stack
final int count = fragmentManager.getBackStackEntryCount();
// 2. If the fragment is **not** "home type", save it to the stack
if( name.equals( FRAGMENT_OTHER) ) {
fragmentTransaction.addToBackStack(name);
}
// Commit !
fragmentTransaction.commit();
// 3. After the commit, if the fragment is not an "home type" the back stack is changed, triggering the
// OnBackStackChanged callback
fragmentManager.addOnBackStackChangedListener(new FragmentManager.OnBackStackChangedListener() {
@Override
public void onBackStackChanged() {
// If the stack decreases it means I clicked the back button
if( fragmentManager.getBackStackEntryCount() <= count){
// pop all the fragment and remove the listener
fragmentManager.popBackStack(FRAGMENT_OTHER, POP_BACK_STACK_INCLUSIVE);
fragmentManager.removeOnBackStackChangedListener(this);
// set the home button selected
navigation.getMenu().getItem(0).setChecked(true);
}
}
});
}
1
投票
投票
试试这个。
BottomNavigationView bottomNavigationView = (BottomNavigationView) findViewById(R.id.navigation);
BottomNavigationViewHelper.disableShiftMode(bottomNavigationView);
1
投票
投票
请试试这个解决方案。我已经对您提供的代码进行了更改。
我假设在第一次你的应用程序将回到主页片段（在你的情况下公告片段）的背面按下，如果你再次按下，应用程序将关闭。
此流程还将反映在底部导航栏中。
public class BottomNavigationViewHelper {
public static void disableShiftMode(BottomNavigationView view) {
BottomNavigationMenuView menuView = (BottomNavigationMenuView) view.getChildAt(0);
try {
Field shiftingMode = menuView.getClass().getDeclaredField("mShiftingMode");
shiftingMode.setAccessible(true);
shiftingMode.setBoolean(menuView, false);
shiftingMode.setAccessible(false);
for (int i = 0; i < menuView.getChildCount(); i++) {
BottomNavigationItemView item = (BottomNavigationItemView) menuView.getChildAt(i);
//noinspection RestrictedApi
item.setShiftingMode(false);
// set once again checked value, so view will be updated
//noinspection RestrictedApi
item.setChecked(item.getItemData().isChecked());
}
} catch (NoSuchFieldException e) {
Log.e("BNVHelper", "Unable to get shift mode field", e);
} catch (IllegalAccessException e) {
Log.e("BNVHelper", "Unable to change value of shift mode", e);
}
}
1
投票
投票
大多数时候，按下后退按钮，后面的堆栈中的旧片段被召回。因此系统调用此onCreateView（）方法
添加此代码
getSupportFragmentManager().addOnBackStackChangedListener(new FragmentManager.OnBackStackChangedListener() {
@Override
public void onBackStackChanged() {
// Gets the previous global stack count
int previousStackCount = mPreviousStackCount;
// Gets a FragmentManager instance
FragmentManager localFragmentManager = getSupportFragmentManager();
// Sets the current back stack count
int currentStackCount = localFragmentManager.getBackStackEntryCount();
// Re-sets the global stack count to be the current count
mPreviousStackCount = currentStackCount;
boolean popping = currentStackCount < previousStackCount;
if(popping){
bottomNavigationView.getMenu().getItem(0).setChecked(true);
}
}
});
1
投票
投票
在尝试了所有内容之后我做到了这一点，最后它起作用-_-。我已经在我的每个活动中粘贴了这个2覆盖方法，我正在通过我的底部导航进行冲浪。
public class MainActivity extends AppCompatActivity {
private static final String BACK_STACK_ROOT_TAG = "root_home_fragment";
private static final String SELECTED_ITEM = "selected_item";
private Fragment fragment;
private FragmentManager fragmentManager;
private BottomNavigationView bottomNavigationView;
private Toolbar toolbar;
private MenuItem menuItemSelected;
private int mMenuItemSelected;
private BottomNavigationView.OnNavigationItemSelectedListener mOnNavigationItemSelectedListener
= new BottomNavigationView.OnNavigationItemSelectedListener() {
@Override
public boolean onNavigationItemSelected(@NonNull MenuItem item) {
boolean selected = false;
switch (item.getItemId()) {
case R.id.action_announcement:
fragment = AnnouncementFragment.newInstance();
selected = true;
break;
case R.id.action_menu:
fragment = MenuFragment.newInstance();
selected = true;
break;
case R.id.action_menu_reports:
fragment = ReportFragment.newInstance();
selected = true;
break;
case R.id.action_setting:
fragment = SettingFragment.newInstance();
selected = true;
}
if(fragment !=null){
fragmentManager = getFragmentManager();
switch (item.getItemId()) {
case R.id.action_announcement:
// Pop every fragment from backstack including home fragment.
fragmentManager.popBackStack(BACK_STACK_ROOT_TAG, FragmentManager.POP_BACK_STACK_INCLUSIVE);
fragmentManager.beginTransaction()
.replace(R.id.content, fragment)
.addToBackStack(BACK_STACK_ROOT_TAG)
.commit();
break;
default:
fragmentManager.beginTransaction()
.replace(R.id.content, fragment)
.addToBackStack(null)
.commit();
break;
}
}
return selected;
}
};
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
bottomNavigationView = (BottomNavigationView) findViewById(R.id.bottom_navigation);
bottomNavigationView.setOnNavigationItemSelectedListener(mOnNavigationItemSelectedListener);
//Always load first fragment as default
bottomNavigationView.setSelectedItemId(R.id.action_announcement);
if (savedInstanceState != null) {
mMenuItemSelected = savedInstanceState.getInt(SELECTED_ITEM, 0);
menuItemSelected = bottomNavigationView.getMenu().findItem(mMenuItemSelected);
} else {
menuItemSelected = bottomNavigationView.getMenu().getItem(0);
}
}
@Override
protected void onSaveInstanceState(Bundle outState) {
outState.putInt(SELECTED_ITEM, mMenuItemSelected);
super.onSaveInstanceState(outState);
}
public void onBackPressed() {
int count = getFragmentManager().getBackStackEntryCount();
if(count >1){
// We have lots of fragment on backstack to be popped.
// Pop till the root fragment.
getFragmentManager().popBackStack(BACK_STACK_ROOT_TAG, FragmentManager.POP_BACK_STACK_INCLUSIVE);
bottomNavigationView.setSelectedItemId(R.id.action_announcement);
}
else{
// Close the application when we are on home fragment.
supportFinishAfterTransition();
}
}
}
1
投票
投票
我有同样的问题，所以我用这个方法解决了我的问题：在我的主要活动中，我有一个底部导航栏和导航抽屉，我需要同步我的抽屉和底部导航中的项目：
我为我的主片段和其他人创建了一个方法：我的主要片段替换器：
val bottomNav = activity?.findViewById<BottomNavigationView>(R.id.activity_main_bottom_navigation)
bottomNav?.selectedItemId = R.id.the_id_of_the_icon__that_represent_the_fragment
这是我的其他片段替换者：
@Override
protected void onResume() {
super.onResume();
bottomNavigationView = (BottomNavigationView) findViewById(R.id.bottom_navigation_Menu_name);
bottomNavigationView.getMenu().getItem(Menu_item_position).setChecked(true);
}
@Override
protected void onRestart() {
super.onRestart();
bottomNavigationView = (BottomNavigationView) findViewById(R.id.bottom_navigation_Menu_name);
bottomNavigationView.getMenu().getItem(Menu_item_position).setChecked(true);
}
所以在那之后，我需要在抽屉和栏中同步项目：注意我使用Mike Penz的材料导航抽屉，以及导航栏的com.ashokvarma.bottomnavigation.BottomNavigationBar。这是为此目的的方法：
public void MainFragmentChanger(final Fragment fragment, final String TAG){
if (main_page_fragment != null){
fragmentTransaction = myFragmentManager.beginTransaction();
fragmentTransaction.remove(main_page_fragment).commit();
}
if (main_drawer.isDrawerOpen()){
main_drawer.closeDrawer();
}
new Handler().post(new Runnable() {
@Override
public void run() {
main_page_fragment = fragment;
main_page_fragment.setRetainInstance(true);
fragmentTransaction = myFragmentManager.beginTransaction();
fragmentTransaction.replace(R.id.main_container, main_page_fragment,TAG);
fragmentTransaction.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_FADE);
fragmentTransaction.commitAllowingStateLoss();
}
});
}
所以我称我的片段像这样：
public void changeBottomFragment(final Fragment fragment, final String TAG){
if (main_drawer.isDrawerOpen()){
main_drawer.closeDrawer();
}
new Handler().post(new Runnable() {
@Override
public void run() {
main_page_fragment = fragment;
main_page_fragment.setRetainInstance(true);
fragmentTransaction = myFragmentManager.beginTransaction();
fragmentTransaction.replace(R.id.main_container, main_page_fragment);
fragmentTransaction.addToBackStack(null);
fragmentTransaction.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_FADE);
fragmentTransaction.commitAllowingStateLoss();
}
});
}
最后，我在片段的onResume方法中调用changeNavAndBarStatus：
public void changeNavAndBarStats(String tag){
if (tag == "flash"){
bottomNavigationBar.selectTab(2,false);
main_drawer.setSelection(flashcards.getIdentifier(),false);
}else if (tag == "dic"){
bottomNavigationBar.selectTab(3,false);
main_drawer.setSelection(dictionary.getIdentifier(),false);
}else if (tag == "Home"){
bottomNavigationBar.selectTab(0,false);
main_drawer.setSelection(home.getIdentifier(),false);
}
}
而已！你已准备好出发！
1
投票
投票
迟到的答案，但在这里。
假设您在MainActivity中有4个片段的BottomNavigation。
- 片段
- FragmentB
- FragmentC
- FragmentD
如果你要将每个片段添加到backstack，如下所示：
用kotlin：
MainFragmentChanger(new MainPageFragment(),"Home");
bottomNavigationBar.selectTab(0,false);
changeBottomFragment(new FlashCardFragment(),"flash");
bottomNavigationBar.selectTab(2,false);
changeBottomFragment(new TranslateFragment(),"dic");
bottomNavigationBar.selectTab(3,false);
你真的不需要在MainActivity中覆盖onBackPressed（），而是显式地对每个片段进行强制转换并像这样分配BottomNavigation：
FragmentA.kt
((MainPageActivity)getContext()).changeNavAndBarStats("flash");
FragmentB.kt
main_bottom_navigation.setOnNavigationItemSelectedListener { item ->
var fragment: Fragment? = null
when (item.itemId) {
R.id.nav_a -> fragment = FragmentA()
R.id.nav_b -> fragment = FragmentB()
R.id.nav_c -> fragment = FragmentC()
R.id.nav_d -> fragment = FragmentD()
}
supportFragmentManager
.beginTransaction()
.setCustomAnimations(R.anim.abc_fade_in, R.anim.abc_fade_out)
.replace(R.id.home_content, fragment!!)
.addToBackStack(fragment.tag)
.commit()
true
}
FragmentC.kt
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
(activity as MainActivity).main_bottom_navigation.menu.getItem(0).isChecked = true
}
片段D.kt
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
(activity as MainActivity).main_bottom_navigation.menu.getItem(1).isChecked = true
}
像这样，片段backstack将正确弹出，甚至在应用程序达到0时退出应用程序。
13
投票
投票
试试这个
@Override
public void onBackPressed() {
BottomNavigationView bottomNavigationView = (BottomNavigationView) findViewById(R.id.navigation);
int seletedItemId = bottomNavigationView.getSelectedItemId();
if (R.id.home != seletedItemId) {
setHomeItem(MainActivity.this);
} else {
super.onBackPressed();
}
}
public static void setHomeItem(Activity activity) {
BottomNavigationView bottomNavigationView = (BottomNavigationView)
activity.findViewById(R.id.navigation);
bottomNavigationView.setSelectedItemId(R.id.home);
}
8
投票
投票
@Override
public void onBackPressed() {
BottomNavigationView mBottomNavigationView = findViewById(R.id.navigation);
if (mBottomNavigationView.getSelectedItemId() == R.id.navigation_home)
{
super.onBackPressed();
finish();
}
else
{
mBottomNavigationView.setSelectedItemId(R.id.navigation_home);
}
}
6
投票
投票
这可能有点晚了，但我认为最好的方法就是这么简单。
@Override
public void onBackPressed() {
if (mBottomNavigationView.getSelectedItemId() == R.id.action_home) {
super.onBackPressed();
} else {
mBottomNavigationView.setSelectedItemId(R.id.action_home);
}
}
我希望它有帮助和快乐编码:)
5
投票
投票
onBackPressed对我不起作用。所以我用过这个。
@Override
protected void onResume() {
super.onResume();
bottomNavigationView.getMenu().getItem(0).setChecked(true);
}
2
投票
投票
最好的方法是：当在主页按钮时，应用程序关闭，当在另一个按钮回到主页按钮时。
下面我把我的代码：
首先我在导航视图中加载主页按钮：
private void loadFragment(Fragment fragment) {
Toast.makeText(this, "load", Toast.LENGTH_SHORT).show();
FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
transaction.replace(R.id.frame_container, fragment, TAG_FRAGMENT);
transaction.commit();
}
并记住不要打电话给qazxsw poi。然后由qazxsw poi处理这种情况：
addToBackStack()1
投票
投票
调用这样的片段时使用addToBackStack方法，
onBackPressed()在onBackPressed方法中使用此代码
@Override
public void onBackPressed() {
if (navigation.getSelectedItemId() == R.id.bottomAkhbar) {
super.onBackPressed();
} else {
navigation.setSelectedItemId(R.id.bottomAkhbar);
}
}
1
投票
投票
根据您的要求，您将使用导航片段，您可以使用带有视图寻呼机的Tablayout并进行底部导航。
getSupportFragmentManager().beginTransaction().addToBackStack(null).add(R.id.content_home_nav,newFragment).commit();
然后使用选项卡布局设置viewpager，并在活动中向tablayout添加图标
if (getSupportFragmentManager().getBackStackEntryCount() > 0 ){
getFragmentManager().popBackStack();
} else {
super.onBackPressed();
}
现在点击tablayout处理所有事情，它将正常工作tabLayout.addOnTabSelectedListener（this）;
1
投票
投票
我遇到了同样的问题，但在这之后我得到了解决方案
首先将此代码粘贴到主活动中（使用底部导航栏的位置）
<android.support.design.widget.TabLayout
android:id="@+id/tab_layout"
android:layout_width="match_parent"
android:layout_height="60dp"></android.support.design.widget.TabLayout>
然后创建一个名为BottomNavigationViewHelper的类并粘贴以下代码。
tabLayout = (TabLayout) findViewById(R.id.tab_layout);
viewPager = (ViewPager) findViewById(R.id.controller_pager);
viewPager.setAdapter(new ViewPagerAdapter(getSupportFragmentManager()));
viewPager.setOffscreenPageLimit(4);
tabLayout.setupWithViewPager(viewPager);
tabLayout.getTabAt(0).setIcon(R.drawable.selector_home);
tabLayout.getTabAt(1).setIcon(R.drawable.selector_contact);
tabLayout.getTabAt(2).setIcon(R.drawable.selector_profile);
tabLayout.getTabAt(3).setIcon(R.drawable.selector_settings);
}
希望能帮助到你
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