如何刷新其活动的 MenuitemSelected 上的片段？

Question

当用户单击菜单操作栏中的刷新图标时，我想刷新片段的内容。

我的应用程序在一个带有视图寻呼机的活动上具有三个片段；我尝试通过在onOptionsItemSelected() 中调用它们来刷新所有这些，并且我对它们执行了事务，当用户单击刷新菜单时应用程序崩溃。

我读过这个问题，它可能和我的相似，但我找不到合适的答案来解决我的问题：android: menu item click event from fragment我也读过这篇文章：但没有任何帮助：https://developer.android.com/guide/topics/ui/menus也许我没有以正确的方式进行。

我在活动中刷新所有三个片段的代码如下：

@Override
public boolean onOptionsItemSelected(MenuItem item){
    Fragment sentMsg=getSupportFragmentManager().findFragmentByTag("fragmentSentMsg");
    Fragment receivedMsg=getSupportFragmentManager().findFragmentByTag("fragmentReceivedMsg");
    Fragment allMsg=getSupportFragmentManager().findFragmentByTag("fragmentAllMsg");
    FragmentTransaction fragmentTransaction=getSupportFragmentManager().beginTransaction();

    switch (item.getItemId()){
        case R.id.refresher_id:
            fragmentTransaction.detach(sentMsg).attach(sentMsg).commit();
            fragmentTransaction.detach(receivedMsg).attach(receivedMsg).commit();
            fragmentTransaction.detach(allMsg).attach(allMsg).commit();

            break;
    }

    return super.onOptionsItemSelected(item);
}

这些是一个片段的代码：

public class Page2_sent_msg extends Fragment {

//default constructor
public Page2_sent_msg(){}

@SuppressLint("ResourceType")
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,Bundle savedInstanceState){
    final View Page2_sent_msg=inflater.inflate(R.layout.page2_sent_msg,container,false);


 ListView sentMsgListView=(ListView)Page2_sent_msg.findViewById(R.id.sentMsgListview);
 ArrayList<String> sentMsgArrayList=new ArrayList<String>();
 SQLite_database_helper_class myDb=new SQLite_database_helper_class(getContext());
 Cursor result=myDb.getting_sms_from_db();
 if (result.moveToFirst()){
     do {
         if (!result.getString(3).equals("Sent message")){
             continue;
         }else{
             sentMsgArrayList.add("SMS No : "+result.getString(0)+"\n"
                     +"Address : "+result.getString(1)+"\n"
                     +"Date : "+result.getString(2)+"\n"
                     +"Type : "+result.getString(3)+"\n"
                     +"Content : "+"\n________\n\n"+result.getString(4)+"\n");
         }
     }while (result.moveToNext());
 }
 ArrayAdapter<String>sentMsgAdapter=new ArrayAdapter<>(getContext(),android.R.layout.simple_list_item_1,sentMsgArrayList);
 sentMsgListView.setAdapter(sentMsgAdapter);
 sentMsgListView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
     @Override
     public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
         //this is what will happen when a user clicks one item from the lis view
     }
 });

 Page2_sent_msg.setTag("sentMsg");


return Page2_sent_msg;
}

我确实需要帮助。亲切的问候！

Answer 1

只需在刷新按钮的onclick中写入片段事务

 fragment = new HomeFragment();
        onFrangmentChange(fragment, true, false);

onFrangmentChange函数会是这样的

    private void onFrangmentChange(BaseFragment fragment, boolean replace, 
  boolean addBackstack) {
    this.fragment = fragment;

    fm = getFragmentManager();

    ft = fm.beginTransaction();
    if (replace) {
        ft.replace(R.id.fragment, fragment);
    } else {
        ft.add(R.id.fragment, fragment);
    }
    if (addBackstack) {
        ft.addToBackStack(fragment.getClass().getSimpleName());
    }
    ft.commit();
}

注意：BaseFragment 只是一个扩展 Fragment 的 Fragment。您可以在这个 Fragment 中编写检查网络连接、电子邮件验证等常用功能。

Answer 2

像这样在片段中添加方法刷新

public void refreshFragment() {
    sentMsgArrayList.clear();
    sentMsgAdapter.notifyDataSetChanged();
    SQLite_database_helper_class myDb=new SQLite_database_helper_class(getContext());
    Cursor result=myDb.getting_sms_from_db();
    if (result.moveToFirst()){
        do {
            if (!result.getString(3).equals("Sent message")){
                 continue;
            }else{
                 sentMsgArrayList.add("SMS No : "+result.getString(0)+"\n"
                 +"Address : "+result.getString(1)+"\n"
                 +"Date : "+result.getString(2)+"\n"
                 +"Type : "+result.getString(3)+"\n"
                 +"Content : "+"\n________\n\n"+result.getString(4)+"\n");
             }
        }while (result.moveToNext());
        sentMsgAdapter.notifyDataSetChanged
   }

然后在用户点击刷新时调用它

@Override
public boolean onOptionsItemSelected(MenuItem item){
Fragment sentMsg=getSupportFragmentManager().findFragmentByTag("fragmentSentMsg");
Fragment receivedMsg=getSupportFragmentManager().findFragmentByTag("fragmentReceivedMsg");
Fragment allMsg=getSupportFragmentManager().findFragmentByTag("fragmentAllMsg");

switch (item.getItemId()){
    case R.id.refresher_id:
        sentMsg.refreshFragment();
        receivedMsg.refreshFragment();
        allMsg.refreshFragment();
        break;
}

return super.onOptionsItemSelected(item);

}