1. Debug 模式查看变量的值；
To quickly evaluate the value of any expression while debugging the program, hold Alt and click this expression to see its value and calculate it, call a method, etc.
2. 自动补全快捷键，默认，自己设置过快捷键以自己的为准：
Use Basic Completion (Ctrl+空格) for completing words in text and comments in files of many different types.
All the words from the current file that start with the typed prefix will appear in the lookup list.
3. 快捷键，查看参数信息，文档：
The shortcuts such as Ctrl+Shift+空格 (View | Quick Documentation), Ctrl+P in default keymap (View | Parameter Info), F3 (Navigate | Declaration) and others can be used not only in the editor but in the code completion popup list as well.
When using Code Completion, you can accept the currently highlighted selection in the popup list with the period character (.), comma (,), semicolon (;), space and other characters.
The selected name is automatically entered in the editor followed by the entered character.
4。 查看最近的修改：
Use Alt+Shift+C in default keymap to quickly review your recent changes to the project.
5. 补全if , do while ,try catch 语句：
Use Ctrl+Shift+Enter to complete a current statement such as if, do-while, try-catch, return (or a method call) into a syntactically correct construct (e.g. add curly braces).
6.Run / Debug快捷键：
By pressing Alt+Shift+F10 you can access the Run/Debug dropdown on the main toolbar, without the need to use your mouse.
7. 关于提交代码：
If you don't want to commit some of your changes to the repository, you can set them aside for a while, by moving to a separate changelist, or by putting them to a shelf. Select such file in the Local tab of the Changes tool window, and on the context menu choose Move to Another Changelist, or Shelve Changes.
8. 查看全局方法：
You can view all methods of the implemented interfaces in a class, if you place the caret at the implements keyword in the class declaration, press Alt+Shift+O, and select the desired interface from the list:
9。 查看一个方法的所以出口：
To view all exit points of a method, place the caret at one of them, e.g. the return statement, and press Alt+Shift+O:
10. 查看每一行代码最近的改变情况：
Version control annotations show the latest changes of each line in one click.
Just right-click an annotation and use the Show Diff command in the context menu.
11. 关于编辑正则表达式：
You can avoid escaping backslashes in your regular expressions. Start typing a regular expression, then press Alt+Enter and choose Edit RegExp. The regular expression opens in a separate tab in the editor, where you can type backslashes as is.
All changes are synchronized with the original regular expression, and escapes are presented automatically. When ready, just press Esc to close the regular expression editor.
12. 使用shell脚本：
You don't need to leave Android Studio to work with your favorite shell. Just click the Terminal tool window button, and enjoy using the embedded local terminal.