按下后如何完美处理底部导航 [英] How to handle bottom navigation perfectly with back pressed
问题描述
我正在使用底部导航栏，但不能完全使用底部导航栏。
I am working on a bottom navigation bar, but I am not getting perfectly bottom navigation bar.
我的 MainActivity 类：
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);
}
我的后背也无法正常工作：
And my back pressed also not working properly:
@Override
public void onBackPressed() {
MenuItem homeItem = bottomNavigationView.getMenu().getItem(0);
if (mMenuItemSelected != homeItem.getItemId()) {
selectFragment(homeItem);
} else {
super.onBackPressed();
}
}
由于底部菜单分布不均，该怎么办在酒吧。如何正确维护菜单空间而又不会分布不均匀。
How should I do that because bottom menu has uneven distribution on bar. How to properly maintain the menu space without uneven distribution.
在这里，我附上我在AVD
Here I am attaching my result which I obtain on AVD
推荐答案
< s>根据材料设计的准则
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。
EDIT: Material Design link no longer mentions back button behavior.
按返回按钮可以退出应用程序，即默认行为，例如在Google照片中……
Pressing the back button you can quit the application, which is the default behavior, such as in Google Photo...
FragmentManager fragmentManager = getFragmentManager();
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
fragmentTransaction.replace(R.id.content, fragment);
// note: there is NOT a addToBackStack call
fragmentTransaction.commit();
...或将用户带到首页部分，然后，如果再次按下，则在出口处
...or lead the user to the home section and then, if pushed again, at the exit.
我个人认为这最后一个模式要好得多。
Personally I find this last pattern much better.
要获得它而没有覆盖 onBackPressed ，您需要识别主片段并将其与其他所有
To get it without override onBackPressed you need to identify the home fragment and differentiate it from all the others
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;
}
});
现在要做的是编写 viewfragment 必须使用的方法
What you have to do now is write the viewfragment method that have to:
- 在<$ c之前知道中有多少个碎片$ c> commit
-
如果片段不是 not home type，则将其保存到$ b之前的堆栈中$ b
提交
- Know how many fragments there are in the stack before the
commit If the fragment is not "home type", save it to the stack before the
commit
添加 OnBackStackChangedListener 当堆栈减少时，
（即当我按回时），删除所有
not home type（ POP_BACK_STACK_INCLUSIVE ），将我们带到首页片段
Add an OnBackStackChangedListener that when the stack decreases,
(i.e. when I pressed back ), delete all the fragments that are
not "home type" (POP_BACK_STACK_INCLUSIVE) , bringing us to the home fragment
在带有注释的完整方法下面
Below the full method with comments
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);
}
}
});
}
这篇关于按下后如何完美处理底部导航的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
