三种语义
- 匿名内部类
- 单例模式
- 伴生对象
定义一个类的同时还创建了对象。
匿名内部类
image.setOnClickListener(object:View.OnClickListener
{
override fun onClick(v:View?){
gotoPreview()
}
})
image.setOnClickListener {
gotoPreview()
}
单例模式
object UserManager{
fun login(){
}
}
- 编译器实现
public final class UserManager{
public static final UserManager INSTANCE；
static{//虚拟机保证它只会被执行一次
UserManager var0 = new UserManager();
INSTANCE = var0;
}
private UserManager(){
}
public void login(){
}
}
- 懒加载
object UserManager{
val user by lazy { loadUser() }
private fun loadUser():User{
return User.create("tom")
}
fun login(){
}
}
- Double Check
class UserManager private constructor(name:String){
compaion object {
@Volatile private var INSTANCE : UserManager? = null;
fun getInstance(name:String):UserManager{
INSTANCE?:synchronized(this){
INSTANCE?:UserManager(name).alse{INSTANCE = it}
}
}
}
}
UserManager.getInstance("Tom")
- 抽象类模板
abstract class BaseSington <in P,out T>{
@Volatile
private var instance :T? = null
protect abstract fun creator(param:P):T{
}
fun getInstance(param:P):T= instance ?:synchronized(this){
instance?:creator(param).alse{ instance = it}
}
}
- 构造传参
伴生对象
1、没有java static关键字
2、定义静态方法和静态变量
class Test{
object InnerPerson{
fun foo(){
}
}
}
Test.InnerPerson.foo()
编译后
public final class Test {
@Metadata(
mv = {1, 4, 3},
bv = {1, 0, 3},
k = 1,
d1 = {"\u0000\u0012\n\u0002\u0018\u0002\n\u0002\u0010\u0000\n\u0002\b\u0002\n\u0002\u0010\u0002\n\u0000\bÆ\u0002\u0018\u00002\u00020\u0001B\u0007\b\u0002¢\u0006\u0002\u0010\u0002J\u0006\u0010\u0003\u001a\u00020\u0004¨\u0006\u0005"},
d2 = {"Lcom/jh/menu/Test$InnerPerson;", "", "()V", "foo", "", "format.PublicComponent"}
)
public static final class InnerPerson {
@NotNull
public static final Test.InnerPerson INSTANCE;
public final void foo() {
}
private InnerPerson() {
}
static {
Test.InnerPerson var0 = new Test.InnerPerson();
INSTANCE = var0;
}
}
}
实际上是通过调用单例InnerPerson的实例上的方法
- 实现类似Java静态方法的代码
