启用动作条按钮选项卡中，每次出现的导航。 [英] Enable an ActionBar Button each time navigation within tabs occurs.

问题描述

我在，我用三个片段指定选项卡的主要活动。我对动作条一个按钮，导航到不同的片段说：关于应用信息一旦用户导航到这个特殊的片段（信息）我禁用它，这样它不会一次又一次地叫。然后在主活动我返回键重新启用它。到现在为止还挺好。但我不能够重新启用一个场景：当用户浏览到的信息片段，并且不preSS回来，但但如果他浏览到不同的标签，信息按钮仍然因为后台禁止说preSS没有被调用。我尝试了很多东西，在onStart（）和片段的onResume（），但我不能引用菜单项中的任何这些，因为我得到一个空指针。

code参考：（MainActivity同时呼吁从onOptionsSelected的信息片段）：

 公共布尔onOptionsItemSelected（菜单项项）{        mMenuItem =项目;
        开关（item.getItemId（））{
        案例R.id.info：
            标签D = getActionBar（）getSelectedTab（）。            的System.out.println（+ d.getText（）的toString（））;
            FragmentManager fragmentManager = getFragmentManager（）;
            FragmentTransaction fragmentTransaction = fragmentManager
                    .beginTransaction（）;            字符串= d.getText（）的toString（）。
            如果（a.equalsIgnoreCase（提醒））{
                FragmentContact fragmentcontact =新FragmentContact（）;
                fragmentTransaction.replace（R.id.realtabcontent，fragmentcontact）;
                mMenuItem.setEnabled（假）;
                //mMenuItem.setIcon(R.drawable.btn_age_01）;
            }
            否则，如果（a.equalsIgnoreCase（通知））{
                FragmentContact fragmentcontact =新FragmentContact（）;
                fragmentTransaction.replace（R.id.realtabcontent2，fragmentcontact）;
                mMenuItem.setEnabled（假）;            }
            否则，如果（a.equalsIgnoreCase（联系人））{
                FragmentContact fragmentcontact =新FragmentContact（）;
                fragmentTransaction.replace（R.id.realtabcontent3，fragmentcontact）;
                mMenuItem.setEnabled（假）;            }
            fragmentTransaction.addToBackStack（NULL）;
            fragmentTransaction.commit（）;            打破;
 

这是返回键（主要活动）：

  @覆盖
    公共无效onBack pressed（）{
        mMenuItem.setEnabled（真）;
        super.onBack pressed（）;
    }
 

解决方案

解决的办法很简单，设置各个碎片的选项菜单使用：

  setHasOptionsMenu（真）;
 

干杯!!

I have a main activity in which I designate tabs using three fragments. I have a button on the ActionBar which navigates to a different fragment say "Info about the app" Once user navigates to this particular fragment (Info) I disable it so that it is not called again and again. Then on the back key in the main activity I re-enable it. So far so good. But I am not able to re-enable it for one scenario: Say if user navigates to the info fragment and does not press back, but however if he navigates to a different tab, the info button is still disabled because back-press has not been called. I tried a lot of things in onStart() and onResume() of fragments but I am not able to reference the menuItem in any of those as I get a null pointer.

Code Reference: (MainActivity while calling the info fragment from onOptionsSelected):

public boolean onOptionsItemSelected(MenuItem item) {

        mMenuItem = item; 
        switch (item.getItemId()) {
        case R.id.info:
            Tab d = getActionBar().getSelectedTab();

            System.out.println(""+d.getText().toString()); 
            FragmentManager fragmentManager = getFragmentManager();  
            FragmentTransaction fragmentTransaction = fragmentManager  
                    .beginTransaction();  

            String a = d.getText().toString(); 
            if(a.equalsIgnoreCase("Reminders")){ 
                FragmentContact fragmentcontact = new FragmentContact(); 
                fragmentTransaction.replace(R.id.realtabcontent, fragmentcontact);  
                mMenuItem.setEnabled(false); 
                //mMenuItem.setIcon(R.drawable.btn_age_01); 
            }
            else if(a.equalsIgnoreCase("Notifications")){
                FragmentContact fragmentcontact = new FragmentContact();
                fragmentTransaction.replace(R.id.realtabcontent2, fragmentcontact);  
                mMenuItem.setEnabled(false); 

            }
            else if(a.equalsIgnoreCase("Contacts")){
                FragmentContact fragmentcontact = new FragmentContact(); 
                fragmentTransaction.replace(R.id.realtabcontent3, fragmentcontact); 
                mMenuItem.setEnabled(false); 

            }
            fragmentTransaction.addToBackStack(null);
            fragmentTransaction.commit();  



            break;

on Back key(Main Activity):

@Override
    public void onBackPressed() {
        mMenuItem.setEnabled(true);
        super.onBackPressed();
    }

解决方案

The solution was very simple, to set an options menu for individual "Fragments" use:

setHasOptionsMenu(true);

Cheers!!

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