Bubble(4)

Login

点击button后，client发出信息给server，server执行sql语句，返回结果集，然后根据结果集判断，再把判断结果返回给client，client得到结果选择弹出提示信息，还是转到下一页。这个看似简单，实际上很复杂的过程是怎么实现的？

1.button的监听代码

private OnClickListener loginconn = new OnClickListener() {public void onClick(View v) {String username = edtUsername.getText().toString();String password = edtPassword.getText().toString();if (username.equals("") || password.equals("")) {Toast.makeText(LoginActivity.this, R.string.non_empty, Toast.LENGTH_LONG).show();return;}// connect to the servernew connectTask().execute("");while(mTcpClient == null || !mTcpClient.isReady());// sends the message to the serverif (mTcpClient != null) {mTcpClient.sendMessage("LOGIN " + username + " " + password);}}};

两个String存储username和password。如果为空提示。如果非空，调用继承于AsyncTask的connectTask.关于AsyncTask，这里有很好的讲解。详解Android中AsyncTask的使用 - scott's blog - 博客频道 - CSDN.NET.开始后台监听，如果mTcpClient一直没有新的响应，一直while等待，一旦不为null,执行sendMessage。所以兵分两路，看看connectTask怎么后台监听，sendmessage执行什么

2.connectTask

public class connectTask extends AsyncTask<String, String, TCPClient> {@Overrideprotected TCPClient doInBackground(String... message) {// we create a TCPClient object andmTcpClient = new TCPClient(new TCPClient.OnMessageReceived() {@Override// here the messageReceived method is implementedpublic void messageReceived(String message) {// this method calls the onProgressUpdatepublishProgress(message);}});mTcpClient.run();return null;}@Overrideprotected void onProgressUpdate(String... values) {super.onProgressUpdate(values);String[] sArray = values[0].split(" ");if (sArray.length == 2) {if (sArray[0].equals("OK")) {// Toast.makeText(MainActivity.this, R.string.login_ok,// Toast.LENGTH_LONG).show();Intent intent = new Intent(LoginActivity.this,TabHostActivity.class);Bundle bundle = new Bundle();bundle.putString("session", sArray[1]);intent.putExtras(bundle);startActivity(intent);mTcpClient.stopClient();}}}}

execute之后，异步任务马上开始，执行doInBackGround. 现在是两个异步任务开始执行，随意会感觉很乱。

package com.example.chatclient;import java.io.BufferedReader;import java.io.BufferedWriter;import java.io.InputStreamReader;import java.io.OutputStreamWriter;import java.io.PrintWriter;import java.net.InetAddress;import java.net.Socket;import android.util.Log;public class TCPClient {private String serverMessage;public static final String SERVERIP = "175.159.81.76"; // your computer IP// addresspublic static final int SERVERPORT = 4445;private OnMessageReceived mMessageListener = null;private boolean mRun = false;PrintWriter out = null;BufferedReader in;/** * Constructor of the class. OnMessagedReceived listens for the messages * received from server */public TCPClient(OnMessageReceived listener) {mMessageListener = listener;}/** * Sends the message entered by client to the server *  * @param message *            text entered by client */public void sendMessage(String message) {if (out != null && !out.checkError()) {out.println(message);out.flush();}}public void stopClient() {mRun = false;}public boolean isReady(){return (out != null);}public void run() {mRun = true;try {// here you must put your computer's IP address.InetAddress serverAddr = InetAddress.getByName(SERVERIP);Log.e("TCP Client", "C: Connecting...");// create a socket to make the connection with the serverSocket socket = new Socket(serverAddr, SERVERPORT);try {// send the message to the serverout = new PrintWriter(new BufferedWriter(new OutputStreamWriter(socket.getOutputStream())), true);Log.e("TCP Client", "C: Sent.");Log.e("TCP Client", "C: Done.");// receive the message which the server sends backin = new BufferedReader(new InputStreamReader(socket.getInputStream()));// in this while the client listens for the messages sent by the// serverwhile (mRun) {serverMessage = in.readLine();Log.e("TCP Client", serverMessage);if (serverMessage != null && mMessageListener != null) {// call the method messageReceived from MyActivity classmMessageListener.messageReceived(serverMessage);}serverMessage = null;}//Log.e("RESPONSE FROM SERVER", "S: Received Message: '"//+ serverMessage + "'");} catch (Exception e) {Log.e("TCP", "S: Error", e);} finally {// the socket must be closed. It is not possible to reconnect to// this socket// after it is closed, which means a new socket instance has to// be created.socket.close();}} catch (Exception e) {Log.e("TCP", "C: Error", e);}}// Declare the interface. The method messageReceived(String message) will// must be implemented in the MyActivity// class at on asynckTask doInBackgroundpublic interface OnMessageReceived {public void messageReceived(String message);}}

程序执行流水图示