android studio 创建第一个app之hello world

 1 package com.demo.my.myapplication;
 2 
 3 import android.support.annotation.Nullable;
 4 import android.support.v7.app.AppCompatActivity;
 5 import android.os.Bundle;
 6 
 7 public class MainActivity extends AppCompatActivity {
 8 
 9     @Override
10     protected void onCreate(@Nullable Bundle savedInstanceState) {
11         super.onCreate(savedInstanceState);
12         setContentView(R.layout.activity_main);
13     }
14 }