【Android】Handler的应用(一):从服务器端加载JSON数据
16lz
2021-01-24
最终目的
以JSON的形式,将数据存入服务器端。 在Android中,以Handler加载显示大批量文字。 在此以加载金庸小说《天龙八部(新修版)》为例(2580480 字节)。以tomcat为服务器,在jsp中以I/O读取本机上的txt文件,写入JSON数据。
在加载过程中,以进度条的形式提示用户需要等待。 加载完成后,进度条消失,并显示加载内容。
Activity文件
package com.app.test02;import java.util.Map;import com.app.util.MyApplication;import android.app.Activity;import android.opengl.Visibility;import android.os.Bundle;import android.os.Handler;import android.os.Message;import android.view.View;import android.widget.Button;import android.widget.ProgressBar;import android.widget.TextView;public class HanderTest_Text extends Activity {private Button button;private TextView textView;private Handler handler;private ProgressBar progressBar;@Overrideprotected void onCreate(Bundle savedInstanceState) {// TODO Auto-generated method stubsuper.onCreate(savedInstanceState);setContentView(R.layout.activity_hander_text);button = (Button) findViewById(R.id.button1);textView = (TextView) findViewById(R.id.textView1);progressBar = (ProgressBar) findViewById(R.id.progressBar1);button.setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View v) {// TODO Auto-generated method stubprogressBar.setVisibility(View.VISIBLE);button.setText("加载中...");new MyThread().start();}});handler = new Handler(){@Overridepublic void handleMessage(Message msg) {// TODO Auto-generated method stubsuper.handleMessage(msg);textView.setText(msg.obj.toString());progressBar.setVisibility(View.GONE);button.setText("加载完成");button.setEnabled(false);}};}class MyThread extends Thread{@Overridepublic void run() {// TODO Auto-generated method stubString result = ApplicationDemo.handleGet("http://10.0.2.2:8888/android/");Map map = ApplicationDemo.getMap(result);Message message = handler.obtainMessage();message.obj = map.get("book");try {sleep(30000);} catch (InterruptedException e) {// TODO Auto-generated catch blocke.printStackTrace();}handler.sendMessage(message);}}}
XML布局文件
activity_hander_text.xml<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="vertical" android:background="#fff" > <LinearLayout android:layout_width="match_parent" android:layout_height="wrap_content" android:orientation="vertical" android:gravity="center"> <Button android:id="@+id/button1" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="加载文本" /> </LinearLayout> <ScrollView android:id="@+id/scrollView1" android:layout_width="match_parent" android:layout_height="wrap_content" > <LinearLayout android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="vertical" > <TextView android:id="@+id/textView1" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="" android:textColor="#000"/> </LinearLayout> </ScrollView> <ProgressBar android:id="@+id/progressBar1" style="?android:attr/progressBarStyleLarge" android:layout_width="wrap_content" android:layout_height="wrap_content" android:visibility="gone" /></LinearLayout>
ApplicationDemo
package com.app.util;import java.util.HashMap;import java.util.Iterator;import java.util.Map;import org.apache.http.HttpResponse;import org.apache.http.HttpStatus;import org.apache.http.client.methods.HttpGet;import org.apache.http.impl.client.DefaultHttpClient;import org.apache.http.util.EntityUtils;import org.json.JSONException;import org.json.JSONObject;import android.app.Application;public class ApplicationDemo extends Application {/** 发送GET请求并获取服务器端返回值 */public static String handleGet(String strUrl) {String result = null;HttpGet request = new HttpGet(strUrl);//实例化get请求DefaultHttpClient client = new DefaultHttpClient();//实例化客户端try {HttpResponse response = client.execute(request);//执行该请求,得到服务器端的响应内容if (response.getStatusLine().getStatusCode() == HttpStatus.SC_OK) {result = EntityUtils.toString(response.getEntity());//把响应结果转成String} else {result = response.getStatusLine().toString();}} catch (Exception e) {return e.getMessage();}return result;}/** 将JSON字符串转换为Map */public static Map<String, Object> getMap(String jsonString) {JSONObject jsonObject;try {jsonObject = new JSONObject(jsonString);@SuppressWarnings("unchecked")Iterator<String> keyIter = jsonObject.keys();String key;Object value;Map<String, Object> valueMap = new HashMap<String, Object>();while (keyIter.hasNext()) {key = keyIter.next();value = jsonObject.get(key);valueMap.put(key, value);}return valueMap;} catch (JSONException e) {e.printStackTrace();}return null;}}
服务器端
在tomcat的\webapps文件夹下新建android文件夹,在其中新建一个index.jsp,用来存放服务器端的JSON数据。index.jsp:
<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8" import="java.util.*" import="java.io.*"%> <%response.setContentType("text/html;charset=utf-8");%><%BufferedReader bReader = null; String line = null; StringBuffer buffer = new StringBuffer(); try { //bReader =new BufferedReader(new FileReader(new File("D:\\Program File\\apache-tomcat-7.0.20\\webapps\\android\\index.jsp"))); bReader =new BufferedReader(new FileReader(new File("E:\\文字\\金庸\\TXT\\新修版\\天龙八部(新修版).txt")));while ((line = bReader.readLine())!=null) { buffer.append(line).append("\n"); } } catch (Exception e) { // TODO: handle exception e.printStackTrace(); } out.print("{\"book\":\"" + buffer.toString() + "\"}");%>
完成后,打开tomcat服务器,在浏览器中输入路径,尝试访问该JSP文件。
如能访问则说明服务器端没问题。
加入权限
由于要访问服务器网络,所以,必须在AndroidManifest.xml中加入网络访问权限:<uses-permission android:name="android.permission.INTERNET"/>
最终效果
加载前
加载过程中
加载完成后
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