这边只说功能的实现，具体观察者模式请自行去了解,因为最近在熟悉kotlin所以以下代码用kotlin书写
首先创建被观察者接口
open interface Observer {
fun update(obj: Object)
}
创建观察者基类
open abstract class Subject {
//被观察者的集合
protected val subjectList = arrayListOf<Observer>()
//注册被观察者，添加到集合
abstract fun register(observer:Observer)
//删除集合
abstract fun unRegister(observer: Observer)
//发送消息
abstract fun notifyObservers(obj: Object)
}
具体观察者实现方法,这里kotlin已经实现了单例
object ConcreteSubject : Subject() {
override fun register(observer: Observer) {
subjectList.add(observer)
}
override fun unRegister(observer: Observer) {
subjectList.remove(observer)
}
//调用集合所有的方法并调用
override fun notifyObservers(obj: Object) {
for (observer in subjectList) {
observer.update(obj)
}
}
}
发送消息页面
class TestActivity :AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_text)
button.setOnClickListener {
finish()
//发送消息
ConcreteSubject.notifyObservers("text发送的消息" as Object)
}
}
}
接收消息，注册，取消注册，这里必须取消注册 否则会出现内存泄漏
class MainActivity : AppCompatActivity() ,Observer{
@RequiresApi(Build.VERSION_CODES.KITKAT)
override fun update(obj: Object) {
tv.setText(obj as String)
}
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
ConcreteSubject.register(this)
button.setOnClickListener {
startActivity(Intent(this,TestActivity::class.java))
}
}
override fun onDestroy() {
super.onDestroy()
ConcreteSubject.unRegister(this)
}
}
class MainActivity : AppCompatActivity() ,Observer{
@RequiresApi(Build.VERSION_CODES.KITKAT)
override fun update(obj: Object) {
tv.setText(obj as String)
}
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
ConcreteSubject.register(this)
button.setOnClickListener {
startActivity(Intent(this,TestActivity::class.java))
}
}
override fun onDestroy() {
super.onDestroy()
ConcreteSubject.unRegister(this)
}
}
