基础语法与组件

Java/Kotlin基础

// Java
String msg = "Hello Android";
System.out.println(msg);

// Kotlin
val msg = "Hello Android"
println(msg)

四大组件简介

• • Activity：界面交互
• • Service：后台服务
• • BroadcastReceiver：广播接收
• • ContentProvider：数据共享

Activity生命周期示例

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
}

@Override
protected void onStart() { super.onStart(); }
@Override
protected void onResume() { super.onResume(); }
@Override
protected void onPause() { super.onPause(); }
@Override
protected void onStop() { super.onStop(); }
@Override
protected void onDestroy() { super.onDestroy(); }