Android开发疫情查询app（实例代码）

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package com.Servlet;

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.Bean.worldbean;
import com.Dao.Dao;
import com.google.gson.Gson;



/**
 * Servlet implementation class Worldservlet
 */
@WebServlet("/Worldservlet")
public class Worldservlet extends HttpServlet {
 private static final long serialVersionUID = 1L;

 /**
 * @see HttpServlet#HttpServlet()
 */
 public Worldservlet() {
 super();
 // TODO Auto-generated constructor stub
 }

 /**
 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
 */
 protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
 // TODO Auto-generated method stub
 response.setContentType("text/html;charset=UTF-8");
 request.setCharacterEncoding("UTF-8");
 String s=null;
 //获取传递过来的参数
 String date = request.getParameter("date");
 String name =request.getParameter("name");
 // Gson 谷歌推出的用于生成和解析JSON 数据格式的工具 使用时需要 导入jar 包 我的是 gson-2.6.2.jar
 Gson gson=new Gson();
 try {
 worldbean info= Dao.getinfo(date,name);
 //将数据 转换为 Json 格式
 s=gson.toJson(info);
 } catch (Exception e) {
 // TODO Auto-generated catch block
 e.printStackTrace();
 }
 //System.out.println(s);
 //方法作用 只能打印输出文本格式的（包括html标签） 不可打印对象
 response.getWriter().write(s);

 }

 /**
 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
 */
 protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
 // TODO Auto-generated method stub
 doGet(request, response);
 }

}

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package com.example.yiqingdemo;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

import org.json.JSONObject;

import java.io.BufferedInputStream;
import java.io.BufferedReader;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;

public class MainActivity extends AppCompatActivity {
 EditText editTextCountry, editTextDate;
 TextView textView;
 Button button;

 @Override
 protected void onCreate(Bundle savedInstanceState) {
 super.onCreate(savedInstanceState);
 setContentView(R.layout.activity_main);
 editTextCountry = findViewById(R.id.editText4);
 editTextDate = findViewById(R.id.editText3);
 textView = findViewById(R.id.textView2);
 button = findViewById(R.id.button);
 button.setOnClickListener(
 new View.OnClickListener() {
  @Override
  public void onClick(View v) {
  //本机tomcat 发布的网站 其实是一个servlet 类 必须先让本机发布（启动tomcat 运行） 然后才能访问改网站
  String url = "http://192.168.0.106:8080/YiQingSearch/Worldservlet?date=" + editTextDate.getText().toString() + "&name=" + editTextCountry.getText().toString();
  get(url);
  }
 }
 );
 }

 public void get(final String url) {
 new Thread(new Runnable() {
 @Override
 public void run() {
 HttpURLConnection connection = null;
 InputStream is = null;


 try {
  //获取url 对象
  URL Url = new URL(url);
  //获取httpURlConnection 对象
  connection = (HttpURLConnection) Url.openConnection();
  //默认为get方法 or post
  connection.setRequestMethod("GET");
  //默认不使用缓存
  connection.setUseCaches(false);
  //设置连接超时时间 单位毫秒
  connection.setConnectTimeout(10000);
  //设置读取超时时间
  connection.setReadTimeout(10000);
  //设置是否从httpUrlConnection 读入，默认为true
  connection.setDoInput(true);

  //相应的码数为 200
  if (connection.getResponseCode() == HttpURLConnection.HTTP_OK) {
  //获取输入流
  is = connection.getInputStream();
  //将输入流内的数据变为Sting类型数据
  String info = getStringFromInputStream(is);
  //转换为JSON 类型便于读取
  JSONObject jsonObject = new JSONObject(info);
  textView.setText(
  "更新时间:" + jsonObject.getString("updatetime") +
   "n确诊人数:" + jsonObject.getString("confirm")
   + "n死亡人数:" + jsonObject.getString("dead")
   + "n治愈人数:" + jsonObject.getString("heal")
  );


  /* //获取url 网页的源代码
  BufferedReader reader= new BufferedReader(new InputStreamReader(is)); //包装字节流为字符流
  StringBuilder response = new StringBuilder();
  String line;


  while((line = reader.readLine())!=null){

  response.append(line);
  }

  String s = response.toString();
  */
  }
 } catch (Exception e) {
  e.printStackTrace();
 } finally {
  if (connection != null) {
  connection.disconnect();
  }
 }

 }
 }).start();

 }

 private static String getStringFromInputStream(InputStream is) throws Exception {
 //定义字节数组缓存区
 ByteArrayOutputStream by = new ByteArrayOutputStream();
 byte[] buff = new byte[1024];
 int len = -1;
 while ((len = is.read(buff)) != -1) {
 by.write(buff, 0, len);
 }
 is.close();
 //将缓冲区的数据转换为 String 类型
 String html = by.toString();
 by.close();
 return html;
 }

}

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<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
 package="com.example.yiqingdemo">

 <uses-permission android:name="android.permission.INTERNET" /> <!--联网所需要的权限-->
 <uses-permission android:name="android.permission.ACCESS_WIFI_STATE" /> <!-- 主要用于管理 WIFI 连接的各方面-->
 <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" /> <!--主要用于监视一般网路连接 -->

 <application
 android:allowBackup="true"
 android:icon="@mipmap/ic_launcher"
 android:label="@string/app_name"
 android:roundIcon="@mipmap/ic_launcher_round"
 android:supportsRtl="true"
 android:theme="@style/AppTheme"
 android:usesCleartextTraffic="true"> <!-- 指示应用程序是否打算使用明文网络流量 -->
 <activity android:name=".MainActivity">
 <intent-filter>
 <action android:name="android.intent.action.MAIN" />

 <category android:name="android.intent.category.LAUNCHER" />
 </intent-filter>
 </activity>
 </application>

</manifest>