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Android開發(fā)疫情查詢app（實(shí)例代碼）

更新時(shí)間：2020年06月10日 17:34:27 作者：碼農(nóng)星雨獸

這篇文章主要介紹了用Android開發(fā)一個(gè)疫情查詢的APP，文中代碼非常詳細(xì)，供大家參考和學(xué)習(xí)，感興趣的朋友可以了解下

一丶工作原理:

App 通過請(qǐng)求本地tomcat發(fā)布的servlet （調(diào)用了 HttpURLConnection 方法）獲取MySQL數(shù)據(jù)庫(kù)當(dāng)中的數(shù)據(jù)，獲取數(shù)據(jù)并返回到App 當(dāng)中，顯示給用戶。（其中傳遞的格式為 json）

使用的工具：Android Studio 開發(fā)APP Eclipse 發(fā)布Servlet，數(shù)據(jù)傳遞

二丶運(yùn)行代碼：

Tomcat 發(fā)布的Servlet 類：

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;
 //獲取傳遞過來(lái)的參數(shù)
 String date = request.getParameter("date");
 String name =request.getParameter("name");
 // Gson 谷歌推出的用于生成和解析JSON 數(shù)據(jù)格式的工具 使用時(shí)需要 導(dǎo)入jar 包 我的是 gson-2.6.2.jar
 Gson gson=new Gson();
 try {
 worldbean info= Dao.getinfo(date,name);
 //將數(shù)據(jù) 轉(zhuǎn)換為 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 只能打印輸出文本格式的（包括html標(biāo)簽） 不可打印對(duì)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);
 }

}

As 當(dāng)中的MainActivity：

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) {
  //本機(jī)tomcat 發(fā)布的網(wǎng)站 其實(shí)是一個(gè)servlet 類 必須先讓本機(jī)發(fā)布（啟動(dòng)tomcat 運(yùn)行） 然后才能訪問改網(wǎng)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 {
  //獲取url 對(duì)象
  URL Url = new URL(url);
  //獲取httpURlConnection 對(duì)象
  connection = (HttpURLConnection) Url.openConnection();
  //默認(rèn)為get方法 or post
  connection.setRequestMethod("GET");
  //默認(rèn)不使用緩存
  connection.setUseCaches(false);
  //設(shè)置連接超時(shí)時(shí)間 單位毫秒
  connection.setConnectTimeout(10000);
  //設(shè)置讀取超時(shí)時(shí)間
  connection.setReadTimeout(10000);
  //設(shè)置是否從httpUrlConnection 讀入，默認(rèn)為true
  connection.setDoInput(true);

  //相應(yīng)的碼數(shù)為 200
  if (connection.getResponseCode() == HttpURLConnection.HTTP_OK) {
  //獲取輸入流
  is = connection.getInputStream();
  //將輸入流內(nèi)的數(shù)據(jù)變?yōu)镾ting類型數(shù)據(jù)
  String info = getStringFromInputStream(is);
  //轉(zhuǎn)換為JSON 類型便于讀取
  JSONObject jsonObject = new JSONObject(info);
  textView.setText(
  "更新時(shí)間:" + jsonObject.getString("updatetime") +
   "\n確診人數(shù):" + jsonObject.getString("confirm")
   + "\n死亡人數(shù):" + jsonObject.getString("dead")
   + "\n治愈人數(shù):" + jsonObject.getString("heal")
  );


  /* //獲取url 網(wǎng)頁(yè)的源代碼
  BufferedReader reader= new BufferedReader(new InputStreamReader(is)); //包裝字節(jié)流為字符流
  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 {
 //定義字節(jié)數(shù)組緩存區(qū)
 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();
 //將緩沖區(qū)的數(shù)據(jù)轉(zhuǎn)換為 String 類型
 String html = by.toString();
 by.close();
 return html;
 }

}

除此之外還需要給APP賦予權(quán)限：

As 的 AndroidMainfest 如下：

添加注釋的為自主添加的權(quán)限

<?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" /> <!--聯(lián)網(wǎng)所需要的權(quán)限-->
 <uses-permission android:name="android.permission.ACCESS_WIFI_STATE" /> <!-- 主要用于管理 WIFI 連接的各方面-->
 <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" /> <!--主要用于監(jiān)視一般網(wǎng)路連接 -->

 <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"> <!-- 指示應(yīng)用程序是否打算使用明文網(wǎng)絡(luò)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>

三丶運(yùn)行結(jié)果：