我的 fragment 和ViewPager
有问题,我的ViewPager
由五个选项卡组成,每个选项卡都是一个 fragment
。
在第一次加载时我对这些加载没有问题,但是当我打开另一个 fragment (在主 fragment 之前),然后返回主要的,我所在的 fragment ,以及那些已被移除(不可见)。
为了解决我需要在中央页面加载之前“离开”两个页面的问题。
一切都只在 API 21 (5.0.1) 和 Android Studio 中。
主要 Activity .java:
public class MainActivity extends FragmentActivity {
private MainActivityFragment frag_MainActivity;
private CreditsFragment frag_Credits;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
frag_MainActivity = new MainActivityFragment(this);
frag_Credits = new CreditsFragment();
switchFrag("main");
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.menu_main, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
int id = item.getItemId();
if (id == R.id.action_home) {
switchFrag("main");
return true;
} else if (id == R.id.action_credits) {
switchFrag("credits");
return true;
}
return super.onOptionsItemSelected(item);
}
public void switchFrag(String view){
Fragment frag = new Fragment();
if(view.equals("main")){
getActionBar().show();
frag = new MainActivityFragment(this);
} else if(view.equals("credits")){
getActionBar().hide();
frag = new CreditsFragment();
}
FragmentManager fragmentManager = getFragmentManager();
fragmentManager.beginTransaction()
.replace(R.id.frame_container, frag)
.addToBackStack(null).commit();
}
@Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
if (keyCode == KeyEvent.KEYCODE_BACK) {
switchFrag("main");
return true;
}
return super.onKeyUp(keyCode, event);
}
public void closeApp() {
finish();
System.exit(0);
}
和 XML(activity_main.xml
):
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/drawer_layout"
android:layout_width="match_parent"
android:layout_height="match_parent">
<FrameLayout
android:id="@+id/frame_container"
android:layout_width="match_parent"
android:layout_height="match_parent">
</FrameLayout>
</RelativeLayout>
MainActivityFragment.java:
public class MainActivityFragment extends Fragment implements ActionBar.TabListener {
private ViewPager viewPager;
private MyAdapter mAdapter;
private ActionBar actionBar;
private String[] tabs = { "Lun", "Mar", "Merc", "Gio", "Ven"};
MainActivity main;
public MainActivityFragment(MainActivity instance) {
main = instance;
}
@Override
public void onViewCreated(View view, Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
viewPager = (ViewPager) main.findViewById(R.id.pager);
actionBar = main.getActionBar();
mAdapter = new MyAdapter(main.getSupportFragmentManager());
viewPager.setAdapter(mAdapter);
actionBar.setHomeButtonEnabled(false);
actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
if(actionBar.getTabCount() == 0){
for (String tab_name : tabs) {
actionBar.addTab(actionBar.newTab().setText(tab_name)
.setTabListener(this));
}
}
viewPager.setOnPageChangeListener(new ViewPager.OnPageChangeListener() {
@Override
public void onPageSelected(int position) {
actionBar.setSelectedNavigationItem(position);
}
@Override
public void onPageScrolled(int arg0, float arg1, int arg2) {
}
@Override
public void onPageScrollStateChanged(int arg0) {
}
});
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
return inflater.inflate(R.layout.fragment_main, container, false);
}
@Override
public void onTabReselected(ActionBar.Tab tab, FragmentTransaction ft) {}
@Override
public void onTabSelected(ActionBar.Tab tab, FragmentTransaction ft) {
viewPager.setCurrentItem(tab.getPosition());
}
@Override
public void onTabUnselected(ActionBar.Tab tab, FragmentTransaction ft) {}
XML(fragment_settings.xml
):
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivityFragment">
<android.support.v4.view.ViewPager
android:id="@+id/pager"
android:layout_width="match_parent"
android:layout_height="match_parent"/>
</RelativeLayout>
如果需要适配器,这里是:
public class MyAdapter extends FragmentPagerAdapter {
public MyAdapter(FragmentManager fm) {
super(fm);
}
@Override
public int getCount() {
return 5;
}
@Override
public android.support.v4.app.Fragment getItem(int position) {
switch(position){
case 0:
return new LunFragment();
case 1:
return new MarFragment();
case 2:
return new MerFragment();
case 3:
return new GioFragment();
case 4:
return new VenFragment();
}
return null;
}
}
最佳答案
将 mAdapter = new MyAdapter(main.getSupportFragmentManager());
替换为 mAdapter = new MyAdapter(main.getChildFragmentManager());
。您需要将 fragment 创建为 MainActivityFragment 的内部 fragment 。
关于java - 不重新加载 fragment ViewPager,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/31612724/