rockwithandroid/net.html at master · beartung/rockwithandroid · GitHub

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>Rock with Android</title>
<link rel="shortcut icon" href="img/favicon.ico">
<link href="css/main.css" type="text/css" rel="stylesheet">
</head>
<body>
<div class="wrapper">
<div class="container">
    <h1>Rock with Android</h1>
    <hr>
	<div class="mod">
		<h3>网络请求</h3>
        <p>移动应用和Ajax很重的前端网站类似，都是用Api和后端打交道，很少有纯粹的单机版App，那种一般都是工具，算不上移动互联网的应用。</p>
        <p>想访问网络，首先要在AndroidManifest.xml中加入访问网络的权限，另外注意：<span class="tip">网络操作要异步进行，不能阻塞UI渲染线程！</span></p>
        <pre class="code">
        &lt;uses-permission android:name="android.permission.INTERNET" /&gt;
        </pre>
        </p>
        <p>安卓框架本身里面有两个用来做网络访问的常用库，感兴趣的同学可以看<a target="_blank" href="http://android-developers.blogspot.jp/2011/09/androids-http-clients.html">Android’s HTTP Clients</a>。这里只说结论，对应安卓2.2之前来讲HttpClient要优于HttpURLConnection，而从2.3向后的版本，HttpURLConnection是比较推荐的选择。</p>
        <h4>HttpClient</h4>
        <p>推荐一个基于Apache的HttpClient的封装库，<a target="_blank" href="https://github.com/loopj/android-async-http">loopj/android-async-http</a>，大家可以试用下。因为loopj的这个库是封装了异步操作的，如果需要自己做异步并且做更多的定制的话，还是要自己来做。不过这个库里提供的RequestParams和SimpleMultipartEntity这两个类很不错，支持处理普通的和multipart上传的form，比较轻便。我一般把用这两个拿出来和自己定制的HttpClient配合用。下面说下HttpClient需要注意的一些点：</p>
        <ol>
        <li>开启GZIP的支持，这样能节省些网络传输的数据量：
        <pre class="code">
    httpClient.addRequestInterceptor(new HttpRequestInterceptor() {
        public void process(HttpRequest request, HttpContext context) {
            if (!request.containsHeader(HEADER_ACCEPT_ENCODING)) {
                request.addHeader(HEADER_ACCEPT_ENCODING, ENCODING_GZIP);
            }
        }
    });

    httpClient.addResponseInterceptor(new HttpResponseInterceptor() {
        public void process(HttpResponse response, HttpContext context) {
            final HttpEntity entity = response.getEntity();
            final Header encoding = entity.getContentEncoding();
            if (encoding != null) {
                for (HeaderElement element : encoding.getElements()) {
                    if (element.getName().equalsIgnoreCase(ENCODING_GZIP)) {
                        response.setEntity(new InflatingEntity(response.getEntity()));
                        break;
                    }
                }
            }
        }
    });
        </pre>
        </li>
        <li>因为很多应用是用的OAuth2认证，并且使用https协议来传输数据的，那么如果你的后端网站的证书配置有问题，或者在某些被改动的ROM或机型上会报https的证书异常。<span class="tip">可以使用信任所有证书的方法避免这一事情，但是前提是你知道后端网站值得信赖！</span>
        <pre class="code">
    public static void setTrustAllFactory(HttpClient httpClient){
        try{
            KeyStore trustStore = KeyStore.getInstance(KeyStore.getDefaultType());
            trustStore.load(null, null);
            SSLSocketFactory sf = new MySSLSocketFactory(trustStore);
            sf.setHostnameVerifier(SSLSocketFactory.ALLOW_ALL_HOSTNAME_VERIFIER);
            setSSLSocketFactory(httpClient, sf);
        }catch (Exception e){
            e.printStackTrace();
        }
    }
        </pre>
        <p>具体这个问题可以参考<a target="_blank" href="http://stackoverflow.com/questions/7622004/android-making-https-request">android-making-https-request</a>，一个典型的MySSLSocketFactory如下。</p>
        <pre class="code">
class MySSLSocketFactory extends SSLSocketFactory {
    SSLContext sslContext = SSLContext.getInstance("TLS");

    public MySSLSocketFactory(KeyStore truststore)
            throws NoSuchAlgorithmException, KeyManagementException,
            KeyStoreException, UnrecoverableKeyException {
        super(truststore);

        TrustManager tm = new X509TrustManager() {
            public void checkClientTrusted(X509Certificate[] chain,
                    String authType) throws CertificateException {
            }

            public void checkServerTrusted(X509Certificate[] chain,
                    String authType) throws CertificateException {
            }

            public X509Certificate[] getAcceptedIssuers() {
                return null;
            }
        };

        sslContext.init(null, new TrustManager[] { tm }, null);
    }

    @Override
    public Socket createSocket(Socket socket, String host, int port,
            boolean autoClose) throws IOException, UnknownHostException {
        return sslContext.getSocketFactory().createSocket(socket, host, port,
                autoClose);
    }

    @Override
    public Socket createSocket() throws IOException {
        return sslContext.getSocketFactory().createSocket();
    }

}
        </pre>
        </li>
        <li>因为移动应用很多时候是走3G/2G的移动网络，所以超时时间需要设长一点，比如20秒。</li>
        </ol>
        <h4>HttpURLConnection</h4>
        <p>推荐基于URLConnection的开源项目：<a target="_blank" href="https://github.com/kevinsawicki/http-request">kevinsawicki/http-request</a>，具体使用可以直接看项目主页的介绍。</p>
        <p class="tip">注意在2.2及以下使用时，需要做下面的处理：</p>
        <pre class="code">
        if (Build.VERSION.SDK_INT &lt; Build.VERSION_CODES.GINGERBREAD) {
            HttpRequest.keepAlive(false);
        }
        </pre>
        <p>具体见<a target="_blank" href="http://developer.android.com/reference/java/net/HttpURLConnection.html">HttpURLConnection</a>的“Avoiding Bugs In Earlier Releases”一节，以及<a target="_blank" href="https://code.google.com/p/android/issues/detail?id=2939">issues#2939</a>。</p>
        <p><a href="index.html">目录</a>｜<a href="data.html">上一章</a>｜<a href="async.html">异步与AyncTask</a></p>
	</div>
</div>
<div class="wrapper-footer"></div>
</div>
<div class="footer">
	<div class="container">
        <a href="https://github.com/beartung/rockwithandroid">RockWithAndroid</a> by <a href="http://github.com/beartung">@Bear</a>
	</div>
</div>
</body>
</html>