1. 概述
有时候在开发中，我们会有一些需求是需要建立长连接的，比如自己项目中的付款码，需要商家用扫码枪来扫二维码，必须等商家扫完二维码收完款时然后发消息给客户端，这个时候就需要让客户端与服务器端建立长连接，达到让客户端与服务器端保持连接，直到收完款然后客户端自行断开连接，同时服务器端也需要在操作成功时候断开连接。
2. 具体实现
1>：添加对okhttp的依赖：
compile 'com.squareup.okhttp3:okhttp:3.8.1'
compile 'com.squareup.okhttp3:mockwebserver:3.8.1'
2>：连接websocket：
/**
* Email: 2185134304@qq.com
* Created by Novate 2018/8/14 16:05
* Version 1.0
* Params:
* Description: 使用OkHttp之Websocket实现长连接
*/
public class TestActivity2 extends BaseActivity {
private RelativeLayout layout_title_left;
@Override
public void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_login);
}
@Override
public void initView() {
layout_title_left = (RelativeLayout) findViewById(R.id.layout_title_left);
layout_title_left.setVisibility(View.VISIBLE);
setListener() ;
}
private long sendTime = 0L;
// 发送心跳包
private Handler mHandler = new Handler();
// 每隔2秒发送一次心跳包，检测连接没有断开
private static final long HEART_BEAT_RATE = 2 * 1000;
// 发送心跳包
private Runnable heartBeatRunnable = new Runnable() {
@Override
public void run() {
if (System.currentTimeMillis() - sendTime >= HEART_BEAT_RATE) {
String message = sendData();
mSocket.send(message);
sendTime = System.currentTimeMillis();
}
mHandler.postDelayed(this, HEART_BEAT_RATE); //每隔一定的时间，对长连接进行一次心跳检测
}
};
private WebSocket mSocket;
private void setListener() {
OkHttpClient mOkHttpClient = new OkHttpClient.Builder()
.readTimeout(3, TimeUnit.SECONDS)//设置读取超时时间
.writeTimeout(3, TimeUnit.SECONDS)//设置写的超时时间
.connectTimeout(3, TimeUnit.SECONDS)//设置连接超时时间
.build();
Request request = new Request.Builder().url("ws://lost:8081/websocket/8").build();
EchoWebSocketListener socketListener = new EchoWebSocketListener();
// 刚进入界面，就开启心跳检测
mHandler.postDelayed(heartBeatRunnable, HEART_BEAT_RATE);
mOkHttpClient.newWebSocket(request, socketListener);
mOkHttpClient.dispatcher().executorService().shutdown();
}
private final class EchoWebSocketListener extends WebSocketListener {
@Override
public void onOpen(WebSocket webSocket, Response response) {
super.onOpen(webSocket, response);
mSocket = webSocket;
// String openid = "1";
//连接成功后，发送登录信息
// String message = sendData();
// mSocket.send(message);
output("连接成功！");
}
@Override
public void onMessage(WebSocket webSocket, ByteString bytes) {
super.onMessage(webSocket, bytes);
output("receive bytes:" + bytes.hex());
}
@Override
public void onMessage(WebSocket webSocket, String text) {
super.onMessage(webSocket, text);
output("服务器端发送来的信息：" + text);
// {"msg":"付款成功","amount":"null","code":"0","qrCode":"123456","data":"cn.pay.entity.QCPOrder@3de382a5","userId":"f"}
// 这里自己用于测试断开连接：就直接在接收到服务器发送的消息后，然后断开连接，然后清除 handler，
//具体可以根据自己实际情况断开连接，比如点击返回键页面关闭时，执行下边逻辑
if (!TextUtils.isEmpty(text)){
if (mSocket != null) {
mSocket .close(1000, null);
}
if (mHandler != null){
mHandler.removeCallbacksAndMessages(null);
mHandler = null ;
}
}
/*//收到服务器端发送来的信息后，每隔2秒发送一次心跳包
final String message = sendHeart();
Timer timer = new Timer();
timer.schedule(new TimerTask() {
@Override
public void run() {
mSocket.send(message);
}
},2000);*/
}
@Override
public void onClosed(WebSocket webSocket, int code, String reason) {
super.onClosed(webSocket, code, reason);
output("closed:" + reason);
}
@Override
public void onClosing(WebSocket webSocket, int code, String reason) {
super.onClosing(webSocket, code, reason);
output("closing:" + reason);
}
@Override
public void onFailure(WebSocket webSocket, Throwable t, Response response) {
super.onFailure(webSocket, t, response);
output("failure:" + t.getMessage());
}
}
private void output(final String text) {
runOnUiThread(new Runnable() {
@Override
public void run() {
Log.e("TAG" , "text: " + text) ;
}
});
}
private String sendData() {
String jsonHead="";
Map<String,Object> mapHead=new HashMap<>();
mapHead.put("qrCode", "123456") ;
jsonHead=buildRequestParams(mapHead);
Log.e("TAG" , "sendData: " + jsonHead) ;
return jsonHead ;
}
public static String buildRequestParams(Object params){
Gson gson=new Gson();
String jsonStr=gson.toJson(params);
return jsonStr;
}
private String sendHeart() {
String jsonHead="";
Map<String,Object> mapHead=new HashMap<>();
mapHead.put("heart", "heart") ;
jsonHead=buildRequestParams(mapHead);
Log.e("TAG" , "sendHeart：" + jsonHead) ;
return jsonHead ;
}
@Override
public void initListener() {
layout_title_left.setOnClickListener(this);
}
@Override
public void initData() {
}
@Override
public void onClick(View v) {
super.onClick(v);
switch (v.getId()){
case R.id.layout_title_left:
/*if (mWebSocket != null) {
mWebSocket.close(1000, null);
}*/
finishActivity(TestActivity2.this);
break;
}
}
@Override
public void onDestroy() {
super.onDestroy();
/*// 清除handler后，就不能再发送数据了
if (mHandler != null) {
mHandler.removeCallbacksAndMessages(null);
mHandler = null;
}*/
/*if (mWebSocket != null) {
mWebSocket.close(1000, null);
}
if (mHandler != null){
mHandler.removeCallbacksAndMessages(null);
mHandler = null ;
}*/
}
}
3. 注意
1>：上边通过handler，每隔5秒时间，给服务器发送一次消息，让服务器端知道自己还活着就可以；
2>：在自己执行完自己操作逻辑之后、或者在 点击返回键时、在onDestroy()方法中，对websocket判断，如果不为空，就关闭连接，然后将其置为null就可以；
3>：给服务器发送数据的地方，就在 心跳包heartBeatRunnable 中的 run()方法发送数据即可，数据格式由服务器端与客户端自己商定就可以，一般就是 json居多就ok；
4>：这里是通过 handler每隔5秒发送一次消息，时间无上限，只要每隔5秒就会发送消息，如果需要的场景是：定义一个 3分钟定时器，每隔5秒发送消息，可以使用 CountDownTimer即可；
