前言
因?yàn)樾枨?可能需要在安卓上完成一個同時包含UDP和TCP的項(xiàng)目。因此，本來做iOS的小編在閑暇之余研究了一波安卓的UDP是如何實(shí)現(xiàn)的。
TCP客戶端實(shí)現(xiàn)請點(diǎn)這里：TCP。
實(shí)現(xiàn)
1.常量設(shè)置
首先,既然要完成UDP,就需要端口和地址。小編想著安卓應(yīng)該有向iOS一樣的(.pch)文件或者是(.h)文件來管理這一類的參數(shù),但是通過谷爹度娘發(fā)現(xiàn),安卓并沒有與(.pch)類似的文件,(.h)文件也不能像iOS一樣直接引用。因此，小編建立了一個類(.java)來設(shè)置常量，用了專門管理這些參數(shù)。如下:
public class Constants {
static final String SOCKET_HOST = "255.255.255.255";
static final int SOCKET_UDP_PORT = 24680;
}
2.UDP的封裝
小編看了很多資料,發(fā)現(xiàn)網(wǎng)上的資料大多數(shù)很復(fù)雜,并不能滿足小編最基礎(chǔ)的需求。因此,小編決定自己封裝一個簡易的類來方便使用。
創(chuàng)建單例
首先,小編想到的是單例。因?yàn)椴还苁莍OS還是安卓,都應(yīng)該有單例。單例的好處主要在于可以使該類在系統(tǒng)內(nèi)存中只存在一個對象，可以節(jié)約系統(tǒng)資源，對于一些需要頻繁創(chuàng)建和銷毀的對象，可以明顯的提高系統(tǒng)的性能。
安卓的單例寫法有很多種,最后小編選擇了一種自己認(rèn)為比較好的寫法,如下：
public class UDPBuild {
private static UDPBuild udpBuild;
private OnUDPReceiveCallbackBlock udpReceiveCallback;
// 構(gòu)造函數(shù)私有化
private UDPBuild() {
super();
}
// 提供一個全局的靜態(tài)方法
public static UDPBuild getUdpBuild() {
if (udpBuild == null) {
synchronized (UDPBuild.class) {
if (udpBuild == null) {
udpBuild = new UDPBuild();
}
}
}
return udpBuild;
}
}
建立線程
為了能更好的處理數(shù)據(jù),小編在這里建立了一個線程。但是安卓的線程和iOS的有一點(diǎn)不太一樣,就是安卓設(shè)備的CPU數(shù)量不太一樣,所以要根據(jù)CPU數(shù)目初始化線程池.如下:
private static final String TAG = "UDPBuild";
// 單個CPU線程池大小
private static final int POOL_SIZE = 5;
private static final int BUFFER_LENGTH = 1024;
private byte[] receiveByte = new byte[BUFFER_LENGTH];
private boolean isThreadRunning = false;
private ExecutorService mThreadPool;
private Thread clientThread;
-------------------------------------------------------------------
private UDPBuild() {
super();
int cpuNumbers = Runtime.getRuntime().availableProcessors();
// 根據(jù)CPU數(shù)目初始化線程池
mThreadPool = Executors.newFixedThreadPool(cpuNumbers * POOL_SIZE);
}
/**
* 開啟發(fā)送數(shù)據(jù)的線程
**/
private void startSocketThread() {
clientThread = new Thread(new Runnable() {
@Override
public void run() {
Log.d(TAG, "clientThread is running...");
}
});
isThreadRunning = true;
clientThread.start();
}
UDP發(fā)送和接收的集成
接下來就是集成UDP的時候了。安卓有兩個類，一個是DatagramSocket,這個類就是安卓代表UDP的Socket;另一個類是DatagramPacket,這個類是安卓接收UDP包的類。所謂的集成就是對這兩個類的使用。
集成的思路是建立一個方法去初始化socket,初始化完后開啟線程,并在線程中加入接收數(shù)據(jù)的方法。在發(fā)送信息時判斷socket存不存在,不存在就使用剛剛說的方法去初始化,初始化完了再發(fā)送。如下:
private DatagramSocket client;
private DatagramPacket receivePacket;
-------------------------------------------------------------------
public void startUDPSocket() {
if (client != null) return;
try {
// 表明這個 Socket 在設(shè)置的端口上監(jiān)聽數(shù)據(jù)。
client = new DatagramSocket(Constants.SOCKET_UDP_PORT);
if (receivePacket == null) {
receivePacket = new DatagramPacket(receiveByte, BUFFER_LENGTH);
}
startSocketThread();
} catch (SocketException e) {
e.printStackTrace();
}
}
/**
* 開啟發(fā)送數(shù)據(jù)的線程
**/
private void startSocketThread() {
clientThread = new Thread(new Runnable() {
@Override
public void run() {
Log.d(TAG, "clientThread is running...");
receiveMessage();
}
});
isThreadRunning = true;
clientThread.start();
}
/**
* 處理接受到的消息
**/
private void receiveMessage() {
while (isThreadRunning) {
if (client != null) {
try {
client.receive(receivePacket);
} catch (IOException e) {
Log.e(TAG, "UDP數(shù)據(jù)包接收失??！線程停止");
e.printStackTrace();
return;
}
}
if (receivePacket == null || receivePacket.getLength() == 0) {
Log.e(TAG, "無法接收UDP數(shù)據(jù)或者接收到的UDP數(shù)據(jù)為空");
continue;
}
String strReceive = new String(receivePacket.getData(), 0, receivePacket.getLength());
Log.d(TAG, strReceive + " from " + receivePacket.getAddress().getHostAddress() + ":" + receivePacket.getPort());
// 每次接收完UDP數(shù)據(jù)后，重置長度。否則可能會導(dǎo)致下次收到數(shù)據(jù)包被截?cái)唷? if (receivePacket != null) {
receivePacket.setLength(BUFFER_LENGTH);
}
}
}
/**
* 發(fā)送信息
**/
public void sendMessage(final String message) {
if (client == null) {
startUDPSocket();
}
mThreadPool.execute(new Runnable() {
@Override
public void run() {
try {
InetAddress targetAddress = InetAddress.getByName(Constants.SOCKET_HOST);
DatagramPacket packet = new DatagramPacket(message.getBytes(), message.length(), targetAddress, Constants.SOCKET_UDP_PORT);
client.send(packet);
} catch (IOException e) {
e.printStackTrace();
}
}
});
}
在接收到數(shù)據(jù)包之后需要將數(shù)據(jù)回調(diào)出去,但是網(wǎng)上大多數(shù)都是把控制器在類中,這不是小編的初衷。因此小編用了一種類似iOS中Block的方式去回調(diào)。如下:
private OnUDPReceiveCallbackBlock udpReceiveCallback;
-------------------------------------------------------------------
public interface OnUDPReceiveCallbackBlock {
void OnParserComplete(DatagramPacket data);
}
public void setUdpReceiveCallback(OnUDPReceiveCallbackBlock callback) {
this.udpReceiveCallback = callback;
}
public void removeCallback(){
udpReceiveCallback = null;
}
/**
* 處理接受到的消息
**/
private void receiveMessage() {
while (isThreadRunning) {
if (client != null) {
try {
client.receive(receivePacket);
} catch (IOException e) {
Log.e(TAG, "UDP數(shù)據(jù)包接收失??！線程停止");
e.printStackTrace();
return;
}
}
if (receivePacket == null || receivePacket.getLength() == 0) {
Log.e(TAG, "無法接收UDP數(shù)據(jù)或者接收到的UDP數(shù)據(jù)為空");
continue;
}
String strReceive = new String(receivePacket.getData(), 0, receivePacket.getLength());
Log.d(TAG, strReceive + " from " + receivePacket.getAddress().getHostAddress() + ":" + receivePacket.getPort());
if (udpReceiveCallback != null) {
udpReceiveCallback.OnParserComplete(receivePacket);
}
// 每次接收完UDP數(shù)據(jù)后，重置長度。否則可能會導(dǎo)致下次收到數(shù)據(jù)包被截?cái)唷? if (receivePacket != null) {
receivePacket.setLength(BUFFER_LENGTH);
}
}
}
既然有開啟UDP,那肯定有關(guān)閉UDP的時候,關(guān)閉UDP時需要接收信息的回調(diào)和線程也移除。注意：在接收包時,有可能因?yàn)閟ocket原因而接收失敗,此時也需要關(guān)閉。這里并不影響下次發(fā)送，因?yàn)橄麓伟l(fā)送時會判斷socket存不存在，不存在會重新建立。如下:
/**
* 處理接受到的消息
**/
private void receiveMessage() {
while (isThreadRunning) {
if (client != null) {
try {
client.receive(receivePacket);
} catch (IOException e) {
Log.e(TAG, "UDP數(shù)據(jù)包接收失??！線程停止");
stopUDPSocket();
e.printStackTrace();
return;
}
}
if (receivePacket == null || receivePacket.getLength() == 0) {
Log.e(TAG, "無法接收UDP數(shù)據(jù)或者接收到的UDP數(shù)據(jù)為空");
continue;
}
String strReceive = new String(receivePacket.getData(), 0, receivePacket.getLength());
Log.d(TAG, strReceive + " from " + receivePacket.getAddress().getHostAddress() + ":" + receivePacket.getPort());
if (udpReceiveCallback != null) {
udpReceiveCallback.OnParserComplete(receivePacket);
}
// 每次接收完UDP數(shù)據(jù)后，重置長度。否則可能會導(dǎo)致下次收到數(shù)據(jù)包被截?cái)唷? if (receivePacket != null) {
receivePacket.setLength(BUFFER_LENGTH);
}
}
}
/**
* 停止UDP
**/
public void stopUDPSocket() {
isThreadRunning = false;
receivePacket = null;
if (clientThread != null) {
clientThread.interrupt();
}
if (client != null) {
client.close();
client = null;
}
removeCallback();
}
到這里，就集成完成了。
3.使用
使用起來相當(dāng)簡單,導(dǎo)入類,初始化,通過該類的方法發(fā)送信息和接收信息即可,如下:
public class MainActivity extends AppCompatActivity {
private UDPBuild udpBuild;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
udpBuild = UDPBuild.getUdpBuild();
udpBuild.setUdpReceiveCallback(new UDPBuild.OnUDPReceiveCallbackBlock() {
@Override
public void OnParserComplete(DatagramPacket data) {
String strReceive = new String(data.getData(), 0, data.getLength());
SimpleDateFormat formatter = new SimpleDateFormat("yyyy年MM月dd日 HH:mm:ss");
Date curDate = new Date(System.currentTimeMillis());
String str = formatter.format(curDate);
//在真機(jī)上運(yùn)行需要用handle回到主線程再更新UI，不然會崩。模擬器上不會
TextView receive = findViewById(R.id.receive_textView);
receive.append(str + ':' + strReceive + '\n');
}
});
}
public void sendMessage(View view) {
EditText editText = findViewById(R.id.send_editText);
String message = editText.getText().toString();
udpBuild.sendMessage(message);
TextView send = findViewById(R.id.send_textView);
send.append(message + '\n');
}
}
到這里為止，UDP的Demo就完成了，寫的不好的地方歡迎大家指出，Demo下載地址：Demo。最后，希望這篇文章對各位看官們有所幫助。對支持小編的看官們表示感謝。
