我有一个Activity,最初是使用FragmentPagerAdapter连接的ViewPager。
当用户在ViewPager的子片段中单击项目时,我使用FragmentTransaction将空容器视图替换为新的Fragment,以便进行导航。
如果在事务上使用addToBackStack(),提交事务然后进行导航回退,则不会返回到ViewPager的视图(初始布局)。
如果在事务上不使用addToBackStack(),提交事务然后导航回退,则应用程序会退出。
显然,ViewPager未添加到后退栈(这并不奇怪,因为它本身不是一个片段)......但是我希望默认行为是按返回键可以返回到活动的初始视图(即ViewPager)。
根据我所了解的,可能是由于发生了片段事务,ViewPager或PagerAdapter失去了应该显示的片段的跟踪。
我真的很困惑,但最终我创建了大量混乱的代码,覆盖了onBackPressed并显示和隐藏viewpager视图。我认为应该有一种更简单的方法来使用默认行为执行适当的导航。
tl; dr
A是托管片段的ViewPager。 B是一个新的片段。
当我用B替换A,然后按返回键,我期望导航回到A,但这并没有发生。
非常感谢任何建议。
代码:
MainActivity:
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
headingLayout = (RelativeLayout) findViewById(R.id.headingLayout);
headingLayout.setVisibility(View.GONE);
// Set up the ViewPager, attaching the adapter and setting up a listener
// for when the
// user swipes between sections.
mViewPager = (ViewPager) findViewById(R.id.pager);
mViewPager.setPageMargin(8);
/** Getting fragment manager */
FragmentManager fm = getSupportFragmentManager();
/** Instantiating FragmentPagerAdapter */
MyFragmentPagerAdapter pagerAdapter = new MyFragmentPagerAdapter(fm);
/** Setting the pagerAdapter to the pager object */
mViewPager.setAdapter(pagerAdapter);
.
.
.
}
public void onListItemClicked(Fragment fragment) {
fromPlayer = false;
InitiateTransaction(fragment, true);
}
public void InitiateTransaction(Fragment fragment, boolean addToBackStack) {
invalidateOptionsMenu();
FragmentManager fm = getSupportFragmentManager();
FragmentTransaction ft = fm.beginTransaction();
ft.replace(R.id.fragmentContainer, fragment).addToBackStack(null)
.commit();
}
PagerAdapter:
package another.music.player;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import another.music.player.fragments.AlbumListFragment;
import another.music.player.fragments.ArtistListFragment;
import another.music.player.fragments.SongListFragment;
public class MyFragmentPagerAdapter extends FragmentPagerAdapter {
final int PAGE_COUNT = 3;
/** Constructor of the class */
public MyFragmentPagerAdapter(FragmentManager fm) {
super(fm);
}
/** This method will be invoked when a page is requested to create */
@Override
public Fragment getItem(int i) {
switch (i) {
case 0:
ArtistListFragment artistListFragment = new ArtistListFragment();
Bundle artistData = new Bundle();
artistData.putInt("current_page", i + 1);
artistListFragment.setArguments(artistData);
return artistListFragment;
case 1:
AlbumListFragment albumListFragment = new AlbumListFragment();
Bundle albumData = new Bundle();
albumData.putInt("current_page", i + 1);
albumData.putBoolean("showHeader", false);
albumListFragment.setArguments(albumData);
return albumListFragment;
default:
SongListFragment songListFragment = new SongListFragment();
Bundle songData = new Bundle();
songData.putInt("current_page", i + 1);
songListFragment.setArguments(songData);
return songListFragment;
}
}
/** Returns the number of pages */
@Override
public int getCount() {
return PAGE_COUNT;
}
@Override
public CharSequence getPageTitle(int position) {
switch (position) {
case 0:
return "Artists";
case 1:
return "Albums";
default:
return "Songs";
}
}
}
主xml文件(包含FragmentContainer和ViewPager):
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/main_layout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@drawable/app_background_ics" >
<RelativeLayout
android:id="@+id/headingLayout"
android:layout_width="match_parent"
android:layout_height="56dp" >
</RelativeLayout>
<FrameLayout
android:id="@+id/fragmentContainer"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:layout_below="@+id/headingLayout" />
<android.support.v4.view.ViewPager
android:id="@+id/pager"
android:layout_width="fill_parent"
android:layout_height="fill_parent" >
<android.support.v4.view.PagerTabStrip
android:id="@+id/pager_title_strip"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="#33b5e5"
android:paddingBottom="4dp"
android:paddingTop="4dp"
android:textColor="#fff" />
</android.support.v4.view.ViewPager>
</RelativeLayout>