首页 > 代码库 > 将访问服务器的工作交由Service承担
将访问服务器的工作交由Service承担
前面的两篇文章里面讲了移动客户端和服务器端的数据交互与显示
但是我们知道Activity是主要负责界面的，那么在activity中不应该承担太多的访问服务器的任务。也就是说，上一篇的文章所讲述的内容，虽然可行。但对于系统的架构来说，还是将责任明确划分。Activity负责界面的显示，而Service负责访问服务器。
本文将展示android端（Activity和Service）的代码，服务器端（servlet）的代码。其数据传递的过程如下：
这一切的大前提是Activity与Service绑定。如果绑定好了以后，数据的传输过程：
1. Activity将数据通过intent传递给Service。这个数据一般是一个查询条件，如（id）
2. Service提取相应的数据值，封装到json中发送request给服务器Servlet
3. Servlet通过查询条件查询结果，并将结果返回给Service
4. Service得到response后提取数据，得到的数据通过一个本地方法（call）或回调方法（callback）将结果传递给Activity
5. Activity通过调用调用Service的方法更新UI
以上就是上图所示的数据传输过程。
代码分为3段，Activity段负责【intent】和【callback】，Service段负责【Json+request+response】，Servlet段负责【query】
/****** Activity.java ******/
package com.example.helloworld;import com.example.service.MsgService;import android.app.Activity;import android.content.ComponentName;import android.content.Context;import android.content.Intent;import android.content.ServiceConnection;import android.os.Bundle;import android.os.IBinder;import android.view.View;import android.view.View.OnClickListener;import android.widget.Button;import android.widget.ProgressBar;import android.widget.TextView;public class ServeActivity extends Activity { private MsgService msgService; private TextView textView; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.fragment_main); textView = (TextView)findViewById(R.id.frag_text); //绑定Service Intent intent = new Intent(ServeActivity.this, MsgService.class); bindService(intent, conn, Context.BIND_AUTO_CREATE); } ServiceConnection conn = new ServiceConnection() { @Override public void onServiceDisconnected(ComponentName name) { } @Override public void onServiceConnected(ComponentName name, IBinder service) { //返回一个MsgService对象 msgService = ((MsgService.MsgBinder)service).getService(); //向Service通过intent传递数据 Intent intent = new Intent(); intent.putExtra("book_name", 1); //启动Service msgService.onStart(intent, 0);//设置回调函数。那么在Service中，直接调用onProgress方法就可以直接执行本段代码 msgService.setOnProgressListener(new OnProgressListener() { @Override public void onProgress(String progress) { // TODO Auto-generated method stub //修改UI textView.setText(progress); } }); } }; @Override protected void onDestroy() { unbindService(conn); super.onDestroy(); }}
这个地方唯一需要注意的就是两段标红的函数。Activity中定义了一个回调函数onProgress，在下面的Service中，只要OnProgressListener的对象调用onProgress这个函数，就相当于是修改了Activity中的UI。这种方法很好用。不过需要先创建一个interface：
package com.example.helloworld;public interface OnProgressListener { void onProgress(String progress);}
回调函数和本篇的大部分实现方法，来自博客 Android Service与Activity之间通信的几种方式 和 一个经典例子让你彻彻底底理解java回调机制
/****** Service.java ********/
package com.example.service;import java.io.BufferedReader;import java.io.InputStream;import java.io.InputStreamReader;import java.net.HttpURLConnection;import org.apache.http.Header;import org.apache.http.HttpEntity;import org.apache.http.HttpResponse;import org.apache.http.client.HttpClient;import org.apache.http.client.methods.HttpPost;import org.apache.http.entity.StringEntity;import org.apache.http.impl.client.DefaultHttpClient;import org.apache.http.message.BasicHeader;import org.apache.http.params.BasicHttpParams;import org.apache.http.params.HttpConnectionParams;import org.apache.http.protocol.HTTP;import org.json.JSONObject;import com.example.helloworld.OnProgressListener;import android.annotation.SuppressLint;import android.app.Service;import android.content.Intent;import android.os.Binder;import android.os.Handler;import android.os.IBinder;import android.os.Looper;import android.os.Message;public class MsgService extends Service { private int index = 2; private String result; private Handler mMainHandler, mChildHandler; int id; private OnProgressListener onProgressListener; public void onStart(Intent intent, int startId){ System.out.println("================="+intent.getIntExtra("book_name", -1)); //获取Activity传过来的数据 id = intent.getIntExtra("book_name", -1); //初始化mMainHandler mMainHandler = new Handler(){ public void handleMessage(Message msg){ //detail1.setBookText((String)msg.obj); result = (String)msg.obj; if(onProgressListener != null){ System.out.println("==========callback function: set the textView text"); //调用Activity中的onProgress方法，修改UI onProgressListener.onProgress((String)msg.obj); } System.out.println("==========main thread get the message:"+msg.obj); System.out.println("Finally, the message is :"+msg.obj); } }; QueryThread thread = new QueryThread(); thread.start(); while(mChildHandler == null){ } if(mChildHandler != null){ //将mChildHandler加入到消息队列中 Message childMsg = mChildHandler.obtainMessage(); childMsg.obj = mMainHandler.getLooper().getThread().getName(); System.out.println("==========send message to mChild: "+childMsg.obj); mChildHandler.sendMessage(childMsg); } } //设置回调函数的接口。Activity通过这个方法获取对象 public void setOnProgressListener(OnProgressListener onProgressListener){ this.onProgressListener = onProgressListener; } public void onDestroy(){ super.onDestroy(); mChildHandler.getLooper().quit(); } public String getBookDetails(int id){ StringBuilder result = new StringBuilder(); String urlStr = "http://192.168.1.21:8080/servletTest/test"; HttpPost post = new HttpPost(urlStr); try{ JSONObject json = new JSONObject(); json.put("book_id", id); System.out.println("=============="+json.toString()); StringEntity se = new StringEntity(json.toString()); se.setContentEncoding((Header) new BasicHeader(HTTP.CONTENT_TYPE, "application/json")); post.setEntity(se); HttpClient httpClient = getHttpClient(); HttpResponse httpResponse = httpClient.execute(post); int httpCode = httpResponse.getStatusLine().getStatusCode(); if(httpCode==HttpURLConnection.HTTP_OK && httpResponse != null){ HttpEntity entity = httpResponse.getEntity(); InputStream inputStream = entity.getContent(); InputStreamReader inputStreamReader = new InputStreamReader(inputStream); BufferedReader reader = new BufferedReader(inputStreamReader); String s; while((s=reader.readLine()) != null){ result.append(s); } reader.close(); JSONObject object = new JSONObject(result.toString()); String str = object.getString("book_list"); //detail1.setBookText(str); return str; } }catch(Exception exception){ exception.printStackTrace(); } return null; } public HttpClient getHttpClient(){ BasicHttpParams httpParams = new BasicHttpParams(); HttpConnectionParams.setConnectionTimeout(httpParams, 5*1000); HttpConnectionParams.setSoTimeout(httpParams, 10*1000); HttpClient client = new DefaultHttpClient(httpParams); return client;} class QueryThread extends Thread{ public void run(){ //初始化消息循环队列，需要在Handler创建之前 Looper.prepare(); mChildHandler = new Handler(){ public void handleMessage(Message msg){ //访问网络等耗时工作 String book_titleString = getBookDetails(id); System.out.println("================book_title from servlet is "+book_titleString); Message toMain = mMainHandler.obtainMessage(); toMain.obj = book_titleString; //向主线程当前线程的Looper对发送message System.out.println("================send message to main thread: "+book_titleString); mMainHandler.sendMessage(toMain); } }; //启动子线程消息循环队列 Looper.loop(); System.out.println("================json is done!"); } } public class MsgBinder extends Binder{ public MsgService getService(){ return MsgService.this; } } @Override public IBinder onBind(Intent arg0) { // TODO Auto-generated method stub return new MsgBinder(); }}
/******* Servlet.java ********/
package com.example.service;import java.io.BufferedReader;import java.io.InputStream;import java.io.InputStreamReader;import java.net.HttpURLConnection;import org.apache.http.Header;import org.apache.http.HttpEntity;import org.apache.http.HttpResponse;import org.apache.http.client.HttpClient;import org.apache.http.client.methods.HttpPost;import org.apache.http.entity.StringEntity;import org.apache.http.impl.client.DefaultHttpClient;import org.apache.http.message.BasicHeader;import org.apache.http.params.BasicHttpParams;import org.apache.http.params.HttpConnectionParams;import org.apache.http.protocol.HTTP;import org.json.JSONObject;import com.example.helloworld.OnProgressListener;import android.annotation.SuppressLint;import android.app.Service;import android.content.Intent;import android.os.Binder;import android.os.Handler;import android.os.IBinder;import android.os.Looper;import android.os.Message;public class MsgService extends Service { private int index = 2; private String result; private Handler mMainHandler, mChildHandler; int id; private OnProgressListener onProgressListener; public void onStart(Intent intent, int startId){ System.out.println("================="+intent.getIntExtra("book_name", -1)); //获取Activity传过来的数据 id = intent.getIntExtra("book_name", -1); //初始化mMainHandler mMainHandler = new Handler(){ public void handleMessage(Message msg){ //detail1.setBookText((String)msg.obj); result = (String)msg.obj; if(onProgressListener != null){ System.out.println("==========callback function: set the textView text"); //调用Activity中的onProgress方法，修改UI onProgressListener.onProgress((String)msg.obj); } System.out.println("==========main thread get the message:"+msg.obj); System.out.println("Finally, the message is :"+msg.obj); } }; QueryThread thread = new QueryThread(); thread.start(); while(mChildHandler == null){ } if(mChildHandler != null){ //将mChildHandler加入到消息队列中 Message childMsg = mChildHandler.obtainMessage(); childMsg.obj = mMainHandler.getLooper().getThread().getName(); System.out.println("==========send message to mChild: "+childMsg.obj); mChildHandler.sendMessage(childMsg); } } //设置回调函数的接口。Activity通过这个方法获取对象 public void setOnProgressListener(OnProgressListener onProgressListener){ this.onProgressListener = onProgressListener; } public void onDestroy(){ super.onDestroy(); mChildHandler.getLooper().quit(); } public String getBookDetails(int id){ StringBuilder result = new StringBuilder(); String urlStr = "http://192.168.1.21:8080/servletTest/test"; HttpPost post = new HttpPost(urlStr); try{ JSONObject json = new JSONObject(); json.put("book_id", id); System.out.println("=============="+json.toString()); StringEntity se = new StringEntity(json.toString()); se.setContentEncoding((Header) new BasicHeader(HTTP.CONTENT_TYPE, "application/json")); post.setEntity(se); HttpClient httpClient = getHttpClient(); HttpResponse httpResponse = httpClient.execute(post); int httpCode = httpResponse.getStatusLine().getStatusCode(); if(httpCode==HttpURLConnection.HTTP_OK && httpResponse != null){ HttpEntity entity = httpResponse.getEntity(); InputStream inputStream = entity.getContent(); InputStreamReader inputStreamReader = new InputStreamReader(inputStream); BufferedReader reader = new BufferedReader(inputStreamReader); String s; while((s=reader.readLine()) != null){ result.append(s); } reader.close(); JSONObject object = new JSONObject(result.toString()); String str = object.getString("book_list"); //detail1.setBookText(str); return str; } }catch(Exception exception){ exception.printStackTrace(); } return null; } public HttpClient getHttpClient(){ BasicHttpParams httpParams = new BasicHttpParams(); HttpConnectionParams.setConnectionTimeout(httpParams, 5*1000); HttpConnectionParams.setSoTimeout(httpParams, 10*1000); HttpClient client = new DefaultHttpClient(httpParams); return client;} class QueryThread extends Thread{ public void run(){ //初始化消息循环队列，需要在Handler创建之前 Looper.prepare(); mChildHandler = new Handler(){ public void handleMessage(Message msg){ //访问网络等耗时工作 String book_titleString = getBookDetails(id); System.out.println("================book_title from servlet is "+book_titleString); Message toMain = mMainHandler.obtainMessage(); toMain.obj = book_titleString; //向主线程当前线程的Looper对发送message System.out.println("================send message to main thread: "+book_titleString); mMainHandler.sendMessage(toMain); } }; //启动子线程消息循环队列 Looper.loop(); System.out.println("================json is done!"); } } public class MsgBinder extends Binder{ public MsgService getService(){ return MsgService.this; } } public int getIndex(){ System.out.println("greg"); return index; } public void startDonwload(){ new Thread(new Runnable() { @Override public void run() { // TODO Auto-generated method stub index++; System.out.println("fd"); } }).start(); } @Override public IBinder onBind(Intent arg0) { // TODO Auto-generated method stub return new MsgBinder(); }}
Bon Appetite~
将访问服务器的工作交由Service承担
声明：以上内容来自用户投稿及互联网公开渠道收集整理发布，本网站不拥有所有权，未作人工编辑处理，也不承担相关法律责任，若内容有误或涉及侵权可进行投诉： 投诉/举报 工作人员会在5个工作日内联系你，一经查实，本站将立刻删除涉嫌侵权内容。