四種分別是callback interface,handler-message,broadcast receiver和observer-subject。
1. callback interface
這種消息傳遞的方式,需要在接收方調用發送方的方法或者在創建實例時,將回調接口傳入,並在接收方實現接口方法。
舉例:
定義一個回調接口:
public interface ITest{
void doWhat();
}
接受方:
public class Receiver implements ITest{
private Sender sender = null;
public void createSender(){
sender = new Sender(this);
}
@Override
public void doWhat(){
//TODO
}
}
發送方:
public class Sender{
private ITest iTest = null;
public Sender(ITest iTest){
this.iTest = iTest;
}
public void doSth(){
iTest.doWhat();
}
}
優點:代碼量小,很容易理解,處理效率高。
缺點:不利於修改和擴展,接口一變更,發送方和接收方都需要修改參數。並且必須提供一個獲取接口的入口。
2. handler-message
這種方式和第一種在構造時有相同之處,就是同樣需要從接收方傳給發送方。
舉例:
接受方:
public class Receiver implements ITest{
private Handler handler = new Handler(new Handler.Callback(){
@Override
public boolean handlerMessage(Message msg){
switch(msg.what){
case 0:
String message = (String)msg.obj;
Log.e("Receiver", message)
break;
case 1:
//TODO
break;
default:
break;
}
return true;
}
});
public void createSender(){
sender = new Sender(handler);
}
}
發送方:
public class Sender{
private Handler handler = null;
public Sender(Handler handler){
this.handler = handler;
}
public void doSth(){
Message msg = new Message();
msg.what = 0;
msg.obj = "Hello world!";
handler.sendMessage(msg);
}
}
優點:無需去自定義接口,便於修改和擴展。
缺點:同樣必須提供一個獲取接口的入口。修改發送方數據後,在接收方存在數據類型轉換異常的風險。
3. broadcast receiver
廣播分動態註冊和靜態註冊,這裏講動態註冊。常用於兩個業務層之間多個數據通信。廣播的本質也是觀察者模式。必須注意的是,爲防止內存泄漏,需要及時註銷接收器。
舉例:
接收方:
public class ReceiverActivity extends AppCompatActivity{
private TestReceiver receiver;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
receiver = new TestReceiver();
IntentFilter filter = new IntentFilter(/*這裏填你自定義的這個廣播過濾的名字NAME*/);
registerReceiver(receiver, filter);
}
@Override
protected void onDestroy() {
super.onDestroy();
//非常重要!!!!!!!!!!
unregisterReceiver(receiver);
}
public class TestReceiver extends BroadcastReceiver {
@Override
public void onReceive(Context context, Intent intent) {
String type = intent.getStringExtra(/*這裏填你自定義的發送消息的類型TYPE*/);
switch(type){
case "TYPE1":
int i = intent.getIntExtra("testInteger", 0);
break;
case "TYPE2":
String s = intent.getStringExtra("testString");
break;
default:
break;
}
}
}
}
發送方:
public class SendService extends Service{
public void doSth1(){
Intent intent = new Intent(/*這裏填剛纔你寫的那個NAME*/);
intent.putExtra(/*這裏填剛纔你寫的那個消息類型TYPE*/,"TYPE1");
intent.putExtra("testInteger", 1);
sendBroadcast(intent);
}
public void doSth2(){
Intent intent = new Intent(/*這裏填剛纔你寫的那個NAME*/);
intent.putExtra(/*這裏填剛纔你寫的那個消息類型TYPE*/,"TYPE2");
intent.putExtra("testString", "Hello world!");
sendBroadcast(intent);
}
}
優點:發送方和接收方實現了完全解耦,發送方將消息發送出去後,這條消息就與他無關了,收沒收到也不管。
缺點:廣播的接收和發送得依賴context的環境。每次調用都需要寫繁瑣的intent和putExtra。數據傳遞方式類比handler,在接收時存在類型轉換異常的風險。
4. observer-subject
觀察者模式常用於一對多的消息羣發。觀察者是接收方,主題是發送方。同樣需要及時註銷防止內存泄漏。
舉例:
定義一個觀察者接口:
public interface Observer{
void newMsg(String msg);
}
定義一個主題接口:
public interface Subject{
void addObserver(Observer observer);
void removeObserver(Observer observer);
void notify(String msg);
}
定義一個觀察者管理類實現主題接口:
public class ObserverManager implements Subject{
private static ObserverManager instance = null;
private List<Observer> Observers = new ArrayList<>();
private ObserverManager(){
}
public static ObserverManager getInstance() {
if (null == instance) {
synchronized (ObserverManager.class) {
if (null == instance) {
instance = new ObserverManager();
}
}
}
return instance;
}
@Override
public void addObserver(Observer observer){
Observers.add(observer);
}
@Override
public void removeObserver(Observer observer){
Observers.remove(observer);
}
@Override
public void notify(String msg){
for(Observer observer: Observers){
observer.newMsg(msg);
}
}
}
觀察者即接收方:
public class ObserverActivity extends AppCompatActivity implements Observer{
private ObserverManager manager = ObserverManager.getInstance();
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
manager.addObserver(this);
}
@Override
protected void onDestroy() {
super.onDestroy();
//非常重要!!!!!!!!!!
manager.removeObserver(this);
}
@Override
public void newMsg(String msg){
Log.e("Get a new msg", msg);
}
}
主題即發送方:
public class Sender{
private ObserverManager manager = ObserverManager.getInstance();
public void sendNewMsg(){
manager.notify("This is a new msg from sender.");
}
}
優點:同廣播,高度解耦。接口自定義,擴展性強。
缺點:一對一時或者接收方數量少時,“殺雞焉用牛刀”。接口修改時需要到處改動,同callback。
原地址:http://blog.csdn.net/zy13608089849/article/details/74766314