获取当前片段的实例在viewpager [英] Getting the current Fragment instance in the viewpager

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本文介绍了获取当前片段的实例在viewpager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code具有 3片段班每个嵌入每个上 ViewPager 。我有一个菜单选项。如图中 onOptionsItemSelected（），通过选择一个选项，我需要更新当前可见的片段。要更新，我要叫这是在片段类中的方法。可有人请建议如何调用该方法？

 公共类MainActivity扩展ActionBarActivity {     ViewPager ViewPager;
     TabsAdapter TabsAdapter;     @覆盖
        公共无效的onCreate（捆绑savedInstanceState）{
            super.onCreate（savedInstanceState）;            ViewPager =新ViewPager（本）;
            ViewPager.setId（R.id.pager）;
            的setContentView（ViewPager）;            最后的动作条酒吧= getSupportActionBar（）;            bar.setNavigationMode（ActionBar.NAVIGATION_MODE_TABS）;            //附加的选项卡片段类和设置选项卡标题。
            TabsAdapter =新TabsAdapter（这一点，ViewPager）;
            TabsAdapter.addTab（bar.newTab（）。的setText（FragmentClass1），
                    FragmentClass1.class，NULL）;
            TabsAdapter.addTab（bar.newTab（）。的setText（FragmentClass2），
              FragmentClass2.class，NULL）;
            TabsAdapter.addTab（bar.newTab（）。的setText（FragmentClass3），
              FragmentClass3.class，NULL）;
            如果（savedInstanceState！= NULL）{
                bar.setSelectedNavigationItem（savedInstanceState.getInt（标签，0））;
            }        }        @覆盖
        公共布尔onOptionsItemSelected（菜单项项）{            开关（item.getItemId（））{            案例R.id.addText：           ** //这里我需要调用它存在于当前可见的片段类中的方法**                    返回true;            }            返回super.onOptionsItemSelected（项目）;
        }
     @覆盖
     保护无效的onSaveInstanceState（捆绑outState）{
      super.onSaveInstanceState（outState）;
            outState.putInt（标签，getSupportActionBar（）getSelectedNavigationIndex（））;     }     公共静态类TabsAdapter扩展FragmentPagerAdapter
      实现ActionBar.TabListener，ViewPager.OnPageChangeListener {      私人最终上下文mContext;
            私人最终动作条mActionBar;
            私人最终ViewPager mViewPager;
            私人最终的ArrayList＆LT; TabInfo＆GT; mTabs =新的ArrayList＆LT; TabInfo＆GT;（）;            静态final类TabInfo {
                私人最终级＆LT;＆GT; CLSS;
                私人最终捆绑ARGS;                TabInfo（类＆LT;＆GT; _class，捆绑_args）{
                    CLSS = _class;
                    ARGS = _args;
                }
            }      公共TabsAdapter（ActionBarActivity活动，ViewPager寻呼机）{
       超级（activity.getSupportFragmentManager（））;
                mContext =活动;
                mActionBar = activity.getSupportActionBar（）;
                mViewPager =寻呼机;
                mViewPager.setAdapter（本）;
                mViewPager.setOnPageChangeListener（本）;
            }      公共无效addTab（ActionBar.Tab标签，类＆LT;＆GT; CLSS，捆绑参数）{
                TabInfo信息=新TabInfo（CLSS，参数）;
                tab.setTag（信息）;
                tab.setTabListener（本）;
                mTabs.add（信息）;
                mActionBar.addTab（标签）;
                notifyDataSetChanged（）;            }      @覆盖
      公共无效onPageScrollStateChanged（INT状态）{
       // TODO自动生成方法存根      }      @覆盖
      公共无效onPageScrolled（INT位置，浮positionOffset，诠释positionOffsetPixels）{
       // TODO自动生成方法存根      }      @覆盖
      公共无效使用onPageSelected（INT位置）{
       // TODO自动生成方法存根
       mActionBar.setSelectedNavigationItem（位置）;
      }      @覆盖
      公共无效onTabReselected（标签选项卡，FragmentTransaction英尺）{
       // TODO自动生成方法存根      }      @覆盖
      公共无效onTabSelected（标签选项卡，FragmentTransaction英尺）{
       对象标记= tab.getTag（）;
                的for（int i = 0; I＆LT; mTab​​s.size（）;我++）{
                    如果（mTabs.get（ⅰ）==标签）{
                        mViewPager.setCurrentItem（ⅰ）;                    }
                }                tabPosition = tab.getPosition（）;
      }      @覆盖
      公共无效onTabUnselected（标签选项卡，FragmentTransaction英尺）{
       // TODO自动生成方法存根      }      @覆盖
      公共片段的getItem（INT位置）{
       TabInfo信息= mTab​​s.get（位置）;
                返回Fragment.instantiate（mContext，info.clss.getName（），info.args）;
      }      @覆盖
      公众诠释的getCount（）{
       返回mTabs.size（）;
      }     }    }

假设下面是该方法的片段类 updateList（）我要打电话：

 公共类FragmentClass1 {    ArrayList的＆LT;串GT; originalData;
    @覆盖
         公共查看onCreateView（LayoutInflater充气器，容器的ViewGroup，
           捆绑savedInstanceState）{          查看fragmentView = inflater.inflate（R.layout.frag1，集装箱，FALSE）;          originalData = getOriginalDataFromDB（）;          返回fragmentView;         }
    公共无效updateList（字符串文本）
    {
       originalData.add（文本）;
       //这里我能做到这一点需要添加其他UI部分
    }
}


解决方案

  

选择一个选项，我需要更新的是片段
  目前可见的。


这样做的一个简单的方法是使用关系到 FragmentPagerAdapter 实施一招：

 情况下R.id.addText：
     片段页= getSupportFragmentManager（）findFragmentByTag（机器人：切换：+ R.id.pager +：+ ViewPager.getCurrentItem（））;
     //基于当前位置，然后，就可以把网页调整
     //类并调用方法：
     如果（ViewPager.getCurrentItem（）== 0安培;＆安培;！页= NULL）{
          （（FragmentClass1）页）.updateList（新项目）;
     }
返回true;

请重新考虑你的变量命名约定，使用作为变量名的类的名称很混乱（所以没有 ViewPager ViewPager ，使用 ViewPager mPager 为例）。

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();
      }

     }

    }

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
    }
}

解决方案

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

A simple way of doing this is using a trick related to the FragmentPagerAdapter implementation:

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;

Please rethink your variable naming convention, using as the variable name the name of the class is very confusing(so no ViewPager ViewPager, use ViewPager mPager for example).

这篇关于获取当前片段的实例在viewpager的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！

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