在 viewpager 中获取当前 Fragment 实例 [英] Getting the current Fragment instance in the viewpager
本文介绍了在 viewpager 中获取当前 Fragment 实例的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
下面是我的代码，其中包含 3 个片段类，每个类都嵌入了 ViewPager 上的 3 个标签中的每一个.我有一个菜单选项.如onOptionsItemSelected() 所示，通过选择一个选项，我需要更新当前可见的片段.要更新我必须调用片段类中的方法.有人可以建议如何调用该方法吗?
Below is my code which has 3 Fragment classes each embedded with each of the 3 tabs on ViewPager. I have a menu option. As shown in the onOptionsItemSelected(), by selecting an option, I need to update the fragment that is currently visible. To update that I have to call a method which is in the fragment class. Can someone please suggest how to call that method?
public class MainActivity extends ActionBarActivity {
ViewPager ViewPager;
TabsAdapter TabsAdapter;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
ViewPager = new ViewPager(this);
ViewPager.setId(R.id.pager);
setContentView(ViewPager);
final ActionBar bar = getSupportActionBar();
bar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
//Attaching the Tabs to the fragment classes and setting the tab title.
TabsAdapter = new TabsAdapter(this, ViewPager);
TabsAdapter.addTab(bar.newTab().setText("FragmentClass1"),
FragmentClass1.class, null);
TabsAdapter.addTab(bar.newTab().setText("FragmentClass2"),
FragmentClass2.class, null);
TabsAdapter.addTab(bar.newTab().setText("FragmentClass3"),
FragmentClass3.class, null);
if (savedInstanceState != null) {
bar.setSelectedNavigationItem(savedInstanceState.getInt("tab", 0));
}
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case R.id.addText:
**// Here I need to call the method which exists in the currently visible Fragment class**
return true;
}
return super.onOptionsItemSelected(item);
}
@Override
protected void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
outState.putInt("tab", getSupportActionBar().getSelectedNavigationIndex());
}
public static class TabsAdapter extends FragmentPagerAdapter
implements ActionBar.TabListener, ViewPager.OnPageChangeListener {
private final Context mContext;
private final ActionBar mActionBar;
private final ViewPager mViewPager;
private final ArrayList<TabInfo> mTabs = new ArrayList<TabInfo>();
static final class TabInfo {
private final Class<?> clss;
private final Bundle args;
TabInfo(Class<?> _class, Bundle _args) {
clss = _class;
args = _args;
}
}
public TabsAdapter(ActionBarActivity activity, ViewPager pager) {
super(activity.getSupportFragmentManager());
mContext = activity;
mActionBar = activity.getSupportActionBar();
mViewPager = pager;
mViewPager.setAdapter(this);
mViewPager.setOnPageChangeListener(this);
}
public void addTab(ActionBar.Tab tab, Class<?> clss, Bundle args) {
TabInfo info = new TabInfo(clss, args);
tab.setTag(info);
tab.setTabListener(this);
mTabs.add(info);
mActionBar.addTab(tab);
notifyDataSetChanged();
}
@Override
public void onPageScrollStateChanged(int state) {
// TODO Auto-generated method stub
}
@Override
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
// TODO Auto-generated method stub
}
@Override
public void onPageSelected(int position) {
// TODO Auto-generated method stub
mActionBar.setSelectedNavigationItem(position);
}
@Override
public void onTabReselected(Tab tab, FragmentTransaction ft) {
// TODO Auto-generated method stub
}
@Override
public void onTabSelected(Tab tab, FragmentTransaction ft) {
Object tag = tab.getTag();
for (int i=0; i<mTabs.size(); i++) {
if (mTabs.get(i) == tag) {
mViewPager.setCurrentItem(i);
}
}
tabPosition = tab.getPosition();
}
@Override
public void onTabUnselected(Tab tab, FragmentTransaction ft) {
// TODO Auto-generated method stub
}
@Override
public Fragment getItem(int position) {
TabInfo info = mTabs.get(position);
return Fragment.instantiate(mContext, info.clss.getName(), info.args);
}
@Override
public int getCount() {
return mTabs.size();
}
}
}
假设下面是具有我想调用的方法 updateList() 的片段类:
Suppose below is the fragment class with the method updateList() I want to call:
public class FragmentClass1{
ArrayList<String> originalData;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View fragmentView = inflater.inflate(R.layout.frag1, container, false);
originalData = getOriginalDataFromDB();
return fragmentView;
}
public void updateList(String text)
{
originalData.add(text);
//Here I could do other UI part that need to added
}
}
推荐答案
public class MyPagerAdapter extends FragmentPagerAdapter {
private Fragment mCurrentFragment;
public Fragment getCurrentFragment() {
return mCurrentFragment;
}
//...
@Override
public void setPrimaryItem(ViewGroup container, int position, Object object) {
if (getCurrentFragment() != object) {
mCurrentFragment = ((Fragment) object);
}
super.setPrimaryItem(container, position, object);
}
}
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