如何在onBackPressed中实现findFragmentById以查找HomeFragment

Question

我正在处理导航抽屉布局中的碎片。每次在frame_container中看到任何其他片段时，我都要按回按钮返回HomeFragment。如果主页片段已经可见，我想完成MainActivity（navigation_drawer_activity）。帮助我纠正主要活动中的OnBackPressed代码。

@Override 
public void onBackPressed() { 
    DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout); 
    if (drawer.isDrawerOpen(GravityCompat.START)) { 
     drawer.closeDrawer(GravityCompat.START); 
    } 

    Fragment fragment = getSupportFragmentManager().findFragmentById(R.id.fragment_home); 
    if(fragment!=null && fragment.isVisible()){ 
     clearBackStack(); 
     finish(); 
    }else { 
     clearBackStack(); 
     getSupportFragmentManager().beginTransaction().replace(R.id.frame_container,new HomeFragment()).commit(); 
    } 

} 

Answer 1

这里是解决方案。我发现了frame_container的片段。 然后检查是否有语句。 if(fragment!=null && fragment instanceof HomeFragment && fragment.isVisible())。这返回home_fragment。 感谢您的回答。

@Override 
public void onBackPressed() { 
    DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout); 
    if (drawer.isDrawerOpen(GravityCompat.START)) { 
     drawer.closeDrawer(GravityCompat.START); 
    } 

    Fragment fragment = getSupportFragmentManager().findFragmentById(R.id.frame_container); 
    if(fragment!=null && fragment instanceof HomeFragment && fragment.isVisible()){ 
     clearBackStack(); 
     finish(); 
    }else { 
     clearBackStack(); 
     getSupportFragmentManager().beginTransaction().replace(R.id.frame_container,new HomeFragment()).commit(); 
    } 

} 

Answer 2

试试这个

@Override 
    public void onBackPressed() { 
     FragmentManager fm = getSupportFragmentManager(); 
     if (drawerLayout.isDrawerOpen(GravityCompat.START)) { 
      drawerLayout.closeDrawer(GravityCompat.START); 
     } else if (fm.getBackStackEntryCount() > 0) { 
      Log.i("MainActivity", "popping backstack"); 
      getSupportFragmentManager().popBackStackImmediate(); 
     } else { 
      Log.i("MainActivity", "nothing on backstack, calling super"); 
      super.onBackPressed(); 
     } 
    }