Android之Http通信——3.Android HTTP请求方式:HttpURLConnection

3.Android HTTP请求方式之HttpURLConnection

引言：

两者的差别:

HttpURLConnection的使用

①使用步骤:

另外除了上面这些外,有时我们还可能须要对响应码进行推断,比方200:

if(conn.getResponseCode( ) != 200)然后一些处理

还有，可能有时我们并不须要传递什么參数，而是直接去訪问一个页面。我们能够直接用：

final InputStream in = new URL(“url”).openStream();

然后直接读流。只是这种方法适合于直接訪问页面的情况。底层实现事实上也是return openConnection().getInputStream()，并且我们还不能设置一些请求头的东东，用不用能够自己掂量掂量

②代码实例：

在開始每一个详细的样例编写前，我们先来编写一个工具类,用于将流转化为二进制数组:

StreamTool.java:

package com.jay.example.utils;
import java.io.ByteArrayOutputStream;
import java.io.InputStream;

public class StreamTool {
//从流中读取数据
public static byte[] read(InputStream inStream) throws Exception{
ByteArrayOutputStream outStream = new ByteArrayOutputStream();
byte[] buffer = new byte[1024];
int len = 0;
while((len = inStream.read(buffer)) != -1)
{
outStream.write(buffer,0,len);
}
inStream.close();
return outStream.toByteArray();
}
}

1.发送GET请求:

好了,那么接下来我们就来写个简单的样例来熟悉HttpURLConnection的使用方法吧:

先看执行的效果。然后我们再看实现代码，执行截图:



恩呢。看完执行效果，我们来開始写代码，我们程序的功能是:

定义了一个上下文菜单，通过点击不同的菜单项，做一些不同的网络请求，

载入图片，载入网页代码，依据代码载入网页到WebView中

由于篇幅原因。直接贴核心代码。要细致研究的能够自行下载代码參考

处理网络请求的类:GetData.java:

package com.jay.example.httpurlconnectiondemo.util;

import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;

public class GetData {
// 定义一个获取网络图片数据的方法:
public static byte[] getImage(String path) throws Exception {
URL url = new URL(path);
HttpURLConnection conn = (HttpURLConnection) url.openConnection();
// 设置连接超时为5秒
conn.setConnectTimeout(5000);
// 设置请求类型为Get类型
conn.setRequestMethod("GET");
// 推断请求Url是否成功
if (conn.getResponseCode() != 200) {
throw new RuntimeException("请求url失败");
}
InputStream inStream = conn.getInputStream();
byte[] bt = StreamTool.read(inStream);
inStream.close();
return bt;
}

// 获取网页的html源码
public static String getHtml(String path) throws Exception {
URL url = new URL(path);
HttpURLConnection conn = (HttpURLConnection) url.openConnection();
conn.setConnectTimeout(5000);
conn.setRequestMethod("GET");
if (conn.getResponseCode() == 200) {
InputStream in = conn.getInputStream();
byte[] data = StreamTool.read(in);
String html = new String(data, "UTF-8");
return html;
}
return null;
}
}

代码非常easy，然后是MainActivity.java:

package com.jay.example.httpurlconnectiondemo;

import com.jay.example.httpurlconnectiondemo.util.GetData;

import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Bundle;
import android.os.Handler;
import android.view.ContextMenu;
import android.view.ContextMenu.ContextMenuInfo;
import android.view.MenuInflater;
import android.view.MenuItem;
import android.view.View;
import android.view.Window;
import android.webkit.WebView;
import android.widget.ImageView;
import android.widget.ScrollView;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends Activity {

private TextView txtMenu, txtshow;
private ImageView imgPic;
private WebView webView;
private ScrollView scroll;
private Bitmap bitmap;
private String detail="";
private boolean flag = false;
private final static String PIC_URL = "http://d.hiphotos.baidu.com/image/pic/item/b03533fa828ba61e0bd9f7ef4534970a304e593e.jpg";
private final static String HTML_URL = "http://www.baidu.com";

// 用于刷新界面
private Handler handler = new Handler() {
public void handleMessage(android.os.Message msg) {
switch (msg.what) {
case 0x001:
hideAllWidget();
imgPic.setVisibility(View.VISIBLE);
imgPic.setImageBitmap(bitmap);
Toast.makeText(MainActivity.this, "图片载入完成", Toast.LENGTH_SHORT).show();
break;
case 0x002:
hideAllWidget();
scroll.setVisibility(View.VISIBLE);
txtshow.setText(detail);
Toast.makeText(MainActivity.this, "HTML代码载入完成", Toast.LENGTH_SHORT).show();
break;
case 0x003:
hideAllWidget();
webView.setVisibility(View.VISIBLE);
webView.loadDataWithBaseURL("",detail, "text/html","UTF-8","");
Toast.makeText(MainActivity.this, "网页载入完成", Toast.LENGTH_SHORT).show();
break;
default:
break;
}
};
};

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
requestWindowFeature(Window.FEATURE_NO_TITLE);
setContentView(R.layout.activity_main);
initView();
setView();
}

private void initView() {
txtMenu = (TextView) findViewById(R.id.txtMenu);
txtshow = (TextView) findViewById(R.id.txtshow);
imgPic = (ImageView) findViewById(R.id.imgPic);
webView = (WebView) findViewById(R.id.webView);
scroll = (ScrollView) findViewById(R.id.scroll);
}

private void setView() {
registerForContextMenu(txtMenu);
//      webView.getSettings().setDefaultTextEncodingName("UTF-8");
}

// 定义一个隐藏全部控件的方法:
private void hideAllWidget() {
imgPic.setVisibility(View.GONE);
scroll.setVisibility(View.GONE);
webView.setVisibility(View.GONE);
}

@Override
// 重写上下文菜单的创建方法
public void onCreateContextMenu(ContextMenu menu, View v, ContextMenuInfo menuInfo) {
MenuInflater inflator = new MenuInflater(this);
inflator.inflate(R.menu.menus, menu);
super.onCreateContextMenu(menu, v, menuInfo);
}

// 上下文菜单被点击是触发该方法
@Override
public boolean onContextItemSelected(MenuItem item) {
switch (item.getItemId()) {
case R.id.one:
new Thread() {
public void run() {
try {
byte[] data = GetData.getImage(PIC_URL);
bitmap = BitmapFactory.decodeByteArray(data, 0, data.length);
} catch (Exception e) {
e.printStackTrace();
}
handler.sendEmptyMessage(0x001);
};
}.start();
break;
case R.id.two:
new Thread() {
public void run() {
try {
detail = GetData.getHtml(HTML_URL);
} catch (Exception e) {
e.printStackTrace();
}
handler.sendEmptyMessage(0x002);
};
}.start();
break;
case R.id.three:
if(detail.equals("")){
Toast.makeText(MainActivity.this, "先请求HTML先嘛~", Toast.LENGTH_SHORT).show();
}else{
handler.sendEmptyMessage(0x003);
}
break;
}
return true;
}

}

注意事项:

2.发送Post请求

有GET自然有POST，我们通过openConnection获取到的HttpURLConnection默认是进行Get请求的,

所以我们使用POST提交数据，应提前设置好相关的參数:conn.setRequestMethod(“POST”);

还有:conn.setDoOutput(true);conn.setDoInput(true);设置同意输入，输出

还有:conn.setUseCaches(false); POST方法不能缓存，要手动设置为false,详细实现看代码:

核心代码:

PostUtils.java

package com.jay.example.httpurlconnectiondemo.util;

import java.io.ByteArrayOutputStream;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.HttpURLConnection;
import java.net.URL;
import java.net.URLEncoder;

public class PostUtils {

public static String LOGIN_URL = "http://172.16.2.54:8080/HttpTest/ServletForPost";

public static String LoginByPost(String number,String passwd)
{
String msg = "";
try{
HttpURLConnection conn = (HttpURLConnection) new URL(LOGIN_URL).openConnection();
//设置请求方式,请求超时信息
conn.setRequestMethod("POST");
conn.setReadTimeout(5000);
conn.setConnectTimeout(5000);
//设置执行输入,输出:
conn.setDoOutput(true);
conn.setDoInput(true);
//Post方式不能缓存,需手动设置为false
conn.setUseCaches(false);
//我们请求的数据:
String data = "passwd="+ URLEncoder.encode(passwd, "UTF-8")+
"&number="+ URLEncoder.encode(number, "UTF-8");
//这里能够写一些请求头的东东...
//获取输出流
OutputStream out = conn.getOutputStream();
out.write(data.getBytes());
out.flush();
if (conn.getResponseCode() == 200) {
// 获取响应的输入流对象
InputStream is = conn.getInputStream();
// 创建字节输出流对象
ByteArrayOutputStream message = new ByteArrayOutputStream();
// 定义读取的长度
int len = 0;
// 定义缓冲区
byte buffer[] = new byte[1024];
// 依照缓冲区的大小，循环读取
while ((len = is.read(buffer)) != -1) {
// 依据读取的长度写入到os对象中
message.write(buffer, 0, len);
}
// 释放资源
is.close();
message.close();
// 返回字符串
msg = new String(message.toByteArray());
return msg;
}
}catch(Exception e){e.printStackTrace();}
return msg;
}
}

执行效果图:

总结:

好的。本节关于HttpURLConnection的内容就到这里，主要介绍了两种不同的请求方式的实现，GET和POST，代码是比較简单的，就多多解释了~另外，另一些复杂的东西。以后有机会再深究…

下节我们来学习的是Apache为我峨嵋你提供的HttpClient。操作会更加简单。敬请期待~

本节代码下载:

Demo下载