通话界面的功能按钮无法显示，要使它显示出来

1、通过AndroidStudio的Layout Inspector查看UI结构

image.png

通过该功能可以基本判断出它位于id为incall_ui_container的incall_pager里面

2、开始跟踪代码

1. incall_screen.xml.xml -->InCallActivity.java --> R.id.main
2. transaction.add(R.id.main, inCallScreen.getInCallScreenFragment(), Tags.IN_CALL_SCREEN);
3. InCallScreen接口，找到它的实现类-->InCallFragment.java
4. layoutInflater.inflate(R.layout.frag_incall_voice, viewGroup, false)); -->找到布局文件 frag_incall_voice.xml
5. frag_incall_voice.xml-->R.id.incall_pager 类型为LockableViewPager.java
6. R.id.incall_pager被设置pager.setAdapter(adapter); 类型为InCallPagerAdapter.java
7. getItem的实现return InCallButtonGridFragment.newInstance(position);
8. 打开InCallButtonGridFragment

 71   @Override
 72   public View onCreateView(
 73       LayoutInflater inflater, @Nullable ViewGroup parent, @Nullable Bundle bundle) {
 74     View view = inflater.inflate(R.layout.incall_button_grid, parent, false);
 75 
 76     buttons[0] = ((CheckableLabeledButton) view.findViewById(R.id.incall_first_button));
 77     buttons[1] = ((CheckableLabeledButton) view.findViewById(R.id.incall_second_button));
 78     buttons[2] = ((CheckableLabeledButton) view.findViewById(R.id.incall_third_button));
 79     buttons[3] = ((CheckableLabeledButton) view.findViewById(R.id.incall_fourth_button));
 80     buttons[4] = ((CheckableLabeledButton) view.findViewById(R.id.incall_fifth_button));
 81     buttons[5] = ((CheckableLabeledButton) view.findViewById(R.id.incall_sixth_button));
 82 
 83     return view;
 84   }