[英]how to set a default fragment at runtime in Navigation drawer that is created by android studio
[英]How to set a default fragment in Android Studio Navigation Drawer?
我正在寻找一种方法来设置导航抽屉中的默认片段,而不是项目#0。我已经看到了一些基于检查saveInstanceState是否为null的解决方案,但是我感觉我无权访问这在我的onNavigationDrawerItemSelected方法中。 这是我的课:
public class Main extends ActionBarActivity
implements NavigationDrawerFragment.NavigationDrawerCallbacks {
/**
* Fragment managing the behaviors, interactions and presentation of the navigation drawer.
*/
private NavigationDrawerFragment mNavigationDrawerFragment;
/**
* Used to store the last screen title. For use in {@link #restoreActionBar()}.
*/
private CharSequence mTitle;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mNavigationDrawerFragment = (NavigationDrawerFragment)
getSupportFragmentManager().findFragmentById(R.id.navigation_drawer);
mTitle = getTitle();
// Set up the drawer.
mNavigationDrawerFragment.setUp(
R.id.navigation_drawer,
(DrawerLayout) findViewById(R.id.drawer_layout));
}
@Override
public void onNavigationDrawerItemSelected(int position) {
// update the Main content by replacing fragments
Fragment fragment = null;
switch (position) {
case 0:
fragment = new HomeFragment();
break;
case 1:
fragment = new HomeFragment();
break;
case 2:
fragment = new HomeFragment();
break;
default:
fragment = new DiscoverFragment();
}
if (fragment != null) {
FragmentManager fragmentManager = getSupportFragmentManager();
fragmentManager.beginTransaction()
.replace(R.id.container, fragment).commit();
}
}
答案很简单。 由于DrawerLayout允许您自己管理片段,因此您只能使用将在常规FragmentActivity中使用的基本FragmentManager API。
我使用以下方法使其更简单一些,即使当前未将任何片段添加到容器中,它也将替换当前片段。 只需使用您要在onCreate()方法中默认设置的片段调用此方法。
public void setFragment(Fragment fragment) {
FragmentManager fragmentManager = getSupportFragmentManager();
fragmentManager.beginTransaction()
.replace(R.id.container, fragment)
.commit();
}
请注意,从技术.add(fragment)
,在第一次调用时使用.add(fragment)
而不是.replace
更为正确,因为您无需替换任何内容,但实际上并不重要,因为在内部,它基本上只是删除所有现有的片段并添加一个使用.add()
为您提供的新工具http://developer.android.com/reference/android/app/FragmentTransaction.html#replace(int,android.app.Fragment,java.lang.String)
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