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android - 在 viewpager 中获取当前 Fragment 实例

转载 作者:IT老高 更新时间:2023-10-28 12:53:28 26 4
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下面是我的代码,其中有 3 个 fragment 类,每个 fragment 类都嵌入了 ViewPager 上的 3 个选项卡中的每一个。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 fragment 。要更新它,我必须调用 fragment 类中的方法。有人可以建议如何调用该方法吗?

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();
}

}

}

假设下面是我要调用的方法 updateList() 的 fragment 类:

 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
}
}

最佳答案

by selecting an option, I need to update the fragment that is currently visible.

一个简单的方法是使用与 FragmentPagerAdapter 实现相关的技巧:

case R.id.addText:
Fragment page = getSupportFragmentManager().findFragmentByTag("android:switcher:" + R.id.pager + ":" + ViewPager.getCurrentItem());
// based on the current position you can then cast the page to the correct
// class and call the method:
if (ViewPager.getCurrentItem() == 0 && page != null) {
((FragmentClass1)page).updateList("new item");
}
return true;

请重新考虑您的变量命名约定,使用类的名称作为变量名非常困惑(因此没有 ViewPager ViewPager,例如使用 ViewPager mPager)。

关于android - 在 viewpager 中获取当前 Fragment 实例,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/18609261/

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