空白活动破坏

Question

我创建了中有一个片段容器中的主要活动的所有片段后表示，我在它的导航菜单选项中选择替代的碎片。它的工作正常，但问题是：

1. 当我点击导航项两次，两个相同的片段打开，我必须按两次后退按钮回去。
2. 当所有碎片，回压破坏后，我看到一个空白页面（可能是主要的活动页面我猜）。

layout_main.xml

<?xml version="1.0" encoding="utf-8"?> 
<android.support.v4.widget.DrawerLayout xmlns:android="http://schemas.android.com/apk/res/android" 
    xmlns:app="http://schemas.android.com/apk/res-auto" 
    xmlns:tools="http://schemas.android.com/tools" 
    android:id="@+id/main_activity_page" 
    android:layout_width="match_parent" 
    android:layout_height="match_parent" 
    android:background="@color/pageBackgroundColor" 
    tools:context="co.sd.app.MainActivity"> 

    <RelativeLayout 
     android:id="@+id/fragment_container" 
     android:layout_width="match_parent" 
     android:layout_height="match_parent" /> 

    <android.support.design.widget.NavigationView 
     android:id="@+id/side_nav_drawer" 
     android:layout_width="wrap_content" 
     android:layout_height="match_parent" 
     android:layout_gravity="start" 
     android:padding="0sp" 
     app:menu="@menu/side_navigation_menu" /> 

</android.support.v4.widget.DrawerLayout> 

MainActivity.java

public class MainActivity extends AppCompatActivity { 

    private Bundle bundle; 
    private SessionManager session; 
    private DrawerLayout drawerLayout; 
    private ActionBarDrawerToggle actionBarToggle; 
    private TextView cartItemCountDisplay; 
    private NavigationView sideNavView; 
    private Menu sideNavViewMenu; 

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

     drawerLayout = (DrawerLayout) findViewById(R.id.main_activity_page); 
     actionBarToggle = new ActionBarDrawerToggle(this, drawerLayout, R.string.OPEN, R.string.CLOSE); 

     drawerLayout.addDrawerListener(actionBarToggle); 
     actionBarToggle.syncState(); 

     getSupportActionBar().setDisplayHomeAsUpEnabled(true); 

     bundle = new Bundle(); 

     sideNavView = ((NavigationView) findViewById(R.id.side_nav_drawer)); 
     sideNavViewMenu = sideNavView.getMenu(); 

     //To Display Home Fragment On Page Load 
     displaySelectedItemResult(sideNavViewMenu.findItem(R.id.nav_home)); 

     //To Adjust Login or Logout option in side navigation menu 
     if (session.isUserLoggedIn()) { 
      sideNavViewMenu.findItem(R.id.nav_login).setVisible(false); 
      sideNavViewMenu.findItem(R.id.nav_logout).setVisible(true); 
     } else { 
      sideNavViewMenu.findItem(R.id.nav_login).setVisible(true); 
      sideNavViewMenu.findItem(R.id.nav_logout).setVisible(false); 
     } 

     //Operation on side navigation item click 
     sideNavView.setNavigationItemSelectedListener(new NavigationView.OnNavigationItemSelectedListener() { 
      @Override 
      public boolean onNavigationItemSelected(MenuItem item) { 
       displaySelectedItemResult(item); 
       //navDrawerLayout.closeDrawers(); 
       return true; 
      } 
     }); 
    } 

    private void displaySelectedItemResult(MenuItem item) { 
     sideNavViewMenu.findItem(R.id.nav_home).setChecked(false); 
     sideNavViewMenu.findItem(R.id.nav_contactUs).setChecked(false); 
     sideNavViewMenu.findItem(R.id.nav_aboutUs).setChecked(false); 
     sideNavViewMenu.findItem(R.id.nav_login).setChecked(false); 
     sideNavViewMenu.findItem(R.id.nav_logout).setChecked(false); 

     Fragment fragment; 

     switch (item.getItemId()) { 
      case R.id.nav_user: 
       if (session.isUserLoggedIn()) { 
        item.setTitle(session.getUserDetails().get(SessionManager.KEY_NAME)); 
       } else { 
        item.setTitle("Login First!"); 
       } 
       drawerLayout.closeDrawer(GravityCompat.START); 
       break; 
      case R.id.nav_home: 
       fragment = new HomeFragment(); 
       if (fragment != null) { 
        callNavMenuItemsFragment(fragment, "FRAG_HOME"); 
       } 
       item.setChecked(true); 
       drawerLayout.closeDrawer(GravityCompat.START); 
       break; 
      case R.id.nav_contactUs: 
       fragment = new ContactUsFragment(); 
       if (fragment != null) { 
        callNavMenuItemsFragment(fragment, "FRAG_CONTACT_US"); 
       } 
       item.setChecked(true); 
       drawerLayout.closeDrawer(GravityCompat.START); 
       break; 
      case R.id.nav_aboutUs: 
       fragment = new AboutUsFragment(); 
       if (fragment != null) { 
        callNavMenuItemsFragment(fragment, "FRAG_ABOUT_US"); 
       } 
       item.setChecked(true); 
       drawerLayout.closeDrawer(GravityCompat.START); 
       break; 
      case R.id.nav_login: 
       new UserAuthentication(MainActivity.this, session).loginAndSignupDialog(); 
       sideNavViewMenu.findItem(R.id.nav_login).setVisible(false); 
       sideNavViewMenu.findItem(R.id.nav_logout).setVisible(true); 
       item.setChecked(true); 
       drawerLayout.closeDrawer(GravityCompat.START); 
       break; 
      case R.id.nav_logout: 
       session.logoutUser(); 
       sideNavViewMenu.findItem(R.id.nav_login).setVisible(true); 
       sideNavViewMenu.findItem(R.id.nav_logout).setVisible(false); 
       item.setChecked(true); 
       drawerLayout.closeDrawer(GravityCompat.START); 
       break; 

      default: 

     } 
    } 

    private FragmentTransaction callNavMenuItemsFragment(final Fragment fragment, final String fragmentTag) { 
     FragmentTransaction ft = getSupportFragmentManager().beginTransaction(); 
     ft.addToBackStack(null); 
     //if (!ACTIVE_FRAGMENT_ID.equals(String.valueOf(fragment.getId()))) { 
     if (!activeFragmentIDsList.contains(String.valueOf(fragment.getId()))) { 
      ft.replace(R.id.fragment_container, fragment, fragmentTag); 
      activeFragmentIDsList.add(String.valueOf(fragment.getId())); 
     } 
     ft.commit(); 
     return ft; 
    } 

    @Override 
    public boolean onOptionsItemSelected(MenuItem item) { 
     if (actionBarToggle.onOptionsItemSelected(item)) { 
      return true; 
     } 
     switch (item.getItemId()) { 
      case android.R.id.home: 
       finish(); 
       break; 
      case R.id.cart: 
       if (session.isUserLoggedIn()) { 
        startActivity(new Intent(MainActivity.this, CartActivity.class)); 
       } else if (new UserAuthentication(MainActivity.this, session).loginAndSignupDialog()) { 
        startActivity(new Intent(MainActivity.this, CartActivity.class)); 
       } 
       break; 

      default: 
     } 
     return super.onOptionsItemSelected(item); 
    } 

    @Override 
    public boolean onCreateOptionsMenu(Menu menu) { 
     getMenuInflater().inflate(R.menu.actionbar_menu, menu); 

     final MenuItem menuItem = menu.findItem(R.id.cart); 
     MenuItemCompat.setActionView(menuItem, R.layout.cart_badge_layout); 
     final View actionView = MenuItemCompat.getActionView(menuItem); 
     cartItemCountDisplay = actionView.findViewById(R.id.cart_badge); 

     setupBadge(); 

     actionView.setOnClickListener(new View.OnClickListener() { 
      @Override 
      public void onClick(View v) { 
       setupBadge(); 
       onOptionsItemSelected(menuItem); 
      } 
     }); 
     return super.onCreateOptionsMenu(menu); 
    } 

    private void setupBadge() { 
     int itemCount = (((AppGlobalContent) getApplicationContext()).getSelectedItemsCount()); 
     if (cartItemCountDisplay != null) { 
      if (itemCount == 0) { 
       if (cartItemCountDisplay.getVisibility() != View.GONE) { 
        cartItemCountDisplay.setVisibility(View.GONE); 
       } 
      } else { 
       cartItemCountDisplay.setText(String.valueOf(Math.min(itemCount, 99))); 
       if (cartItemCountDisplay.getVisibility() != View.VISIBLE) { 
        cartItemCountDisplay.setVisibility(View.VISIBLE); 
       } 
      } 
     } 
    } 

    @Override 
    public void onBackPressed() { 
     if (drawerLayout.isDrawerOpen(GravityCompat.START)) { 
      drawerLayout.closeDrawer(GravityCompat.START); 
     } else { 
      super.onBackPressed(); 
     } 
    } 
} 

请建议我在此。

Answer 1

这将解决您的第二个问题，当你片段加入您的容器，他们将被添加到堆栈，

if (getSupportFragmentManager().getBackStackEntryCount() == 1) { 
      finish(); 
     } 
     else { 
      super.onBackPressed(); 
     } 

所以当堆栈条目数为1，你必须完成的活动。

对于您必须使用“弹回栈”，同时又添加相同片段的第一个问题用：getSupportFragmentManager().popBackStack();