本文關(guān)鍵詞：精通Android3，由筆耕文化傳播整理發(fā)布。

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精通Android3筆記--第十一章

2011-11-30 09:12:28

標(biāo)簽：

1、Android附帶了Apache的HttpClient用于HTTP交互。

2、HttpClient Get程序

      public class HttpGetDemo extends Activity {

@Override

public void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.main);

BufferedReader in = null;

try {

HttpClient client = new DefaultHttpClient();

HttpGet request = new HttpGet("");

HttpResponse response = client.execute(request);

in = new BufferedReader(new InputStreamReader(response

.getEntity().getContent()));

StringBuffer sb = new StringBuffer("");

String line = "";

String NL = System.getProperty("line.separator");

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

sb.append(line + NL);

}

in.close();

String page = sb.toString();

System.out.println(page);

} catch (Exception e) {

e.printStackTrace();

} finally {

if (in != null) {

try {

in.close();

} catch (IOException e) {

e.printStackTrace();

}

}

}

}

}

        HttpClient不附加到activity上，并且應(yīng)該作為一個(gè)獨(dú)立的類來(lái)使用它。

2、用Get方法傳遞參數(shù)，URL的長(zhǎng)度應(yīng)該控制在2048個(gè)字符以內(nèi)

      HttpGet request = new HttpGet("?one=valueGoesHere");

      client.execute(request);

3、Post方法

      HttpClient client = new DefaultHttpClient();

      HttpPost request = new HttpPost("");

      List<NameValuePair> postParameters = new ArrayList<NameValuePair>();

      postParameters.add(new BasicNameValuePair("first","param value one"));

      postParameters.add(new BasicNameValuePair("issuenum", "10317"));

      postParameters.add(new BasicNameValuePair("username", "dave"));

      UrlEncodedFormEntity formEntity = new UrlEncodedFormEntity(postParameters);

      request.setEntity(formEntity);

      HttpResponse response = client.execute(request);      

4、多部分POST，Android本身不支持，可以下載以下jar包

      

      以下網(wǎng)站也有相應(yīng)的項(xiàng)目

      􀀁 Commons IO:

      􀀁 Mime4j:

      􀀁 HttpMime: (inside of HttpClient)

       多部分POST代碼：

       public void executeMultipartPost() throws Exception {

try {

InputStream is = this.getAssets().open("data.xml");

HttpClient httpClient = new DefaultHttpClient();

HttpPost postRequest = new HttpPost(

"");

byte[] data = IOUtils.toByteArray(is);

InputStreamBody isb = new InputStreamBody(

new ByteArrayInputStream(data), "uploadedFile");

StringBody sb1 = new StringBody("some text goes here");

StringBody sb2 = new StringBody("some text goes here too");

MultipartEntity multipartContent = new MultipartEntity();

multipartContent.addPart("uploadedFile", isb);

multipartContent.addPart("one", sb1);

multipartContent.addPart("two", sb2);

postRequest.setEntity(multipartContent);

HttpResponse response = httpClient.execute(postRequest);

response.getEntity().getContent().close();

} catch (Throwable e) {

// handle exception here

}

}

5、Android本身不支持SOAP，可從以下網(wǎng)站尋找相關(guān)資源：

      

     

6、Android支持JSON

7、HTTP中可能發(fā)生的異常：網(wǎng)絡(luò)連接異常，協(xié)議異常如身份驗(yàn)證錯(cuò)誤，無(wú)效的cookie等。例如，如果必須在HTTP請(qǐng)求中提供登錄憑證但未成功，則可能看到協(xié)議異常。對(duì)于HTTP調(diào)用，超時(shí)包含兩個(gè)方面：連接超時(shí)和套接字超時(shí)，其中套接字超時(shí)為HttpClient可以連接到服務(wù)器，，但是在規(guī)定時(shí)間內(nèi)未接收到響應(yīng)。

8、HttpClient簡(jiǎn)單的重試代碼：

      public class TestHttpGet {

public String executeHttpGetWithRetry() throws Exception {

int retry = 3;

int count = 0;

while (count < retry) {

count += 1;

try {

String response = executeHttpGet();

/**

* if we get here, that means we were successful and we can

* stop.

*/

return response;

} catch (Exception e) {

/**

* if we have exhausted our retry limit

*/

if (count < retry) {

/**

* we have retries remaining, so log the message and go

* again.

*/

System.out.println(e.getMessage());

} else {

System.out.println("all retries failed");

throw e;

}

}

}

return null;

}

 

public String executeHttpGet() throws Exception {

BufferedReader in = null;

try {

HttpClient client = new DefaultHttpClient();

HttpGet request = new HttpGet("");

HttpResponse response = client.execute(request);

in = new BufferedReader(new InputStreamReader(response

.getEntity().getContent()));

StringBuffer sb = new StringBuffer("");

String line = "";

String NL = System.getProperty("line.separator");

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

sb.append(line + NL);

}

in.close();

String result = sb.toString();

return result;

} finally {

if (in != null) {

try {

in.close();

} catch (IOException e) {

e.printStackTrace();

}

}

}

}

9、在實(shí)際應(yīng)用中，應(yīng)該為整個(gè)應(yīng)用程序創(chuàng)建一個(gè)HttpClient，并將其用于所有HTTP通信。此時(shí)就要考慮同時(shí)發(fā)出多個(gè)請(qǐng)求的多線程問(wèn)題，Android中已經(jīng)有了相關(guān)方法，即使用ThreadSafeClientConnManager創(chuàng)建DefaultHttpClient：

      public class CustomHttpClient {

private static HttpClient customHttpClient;

 

/** A private Constructor prevents instantiation */

private CustomHttpClient() {

}

 

public static synchronized HttpClient getHttpClient() {

if (customHttpClient == null) {

HttpParams params = new BasicHttpParams();

HttpProtocolParams.setVersion(params, HttpVersion.HTTP_1_1);

HttpProtocolParams.setContentCharset(params,

HTTP.DEFAULT_CONTENT_CHARSET);

HttpProtocolParams.setUseExpectContinue(params, true);

HttpProtocolParams.setUserAgent(params,

"Mozilla/5.0 (Linux; U; Android 2.2.1; en-us; Nexus One Build/FRG83) AppleWebKit/533.1

(KHTML, like Gecko) Version/4.0 Mobile Safari/533.1"

);

ConnManagerParams.setTimeout(params, 1000);

HttpConnectionParams.setConnectionTimeout(params, 5000);

HttpConnectionParams.setSoTimeout(params, 10000);

SchemeRegistry schReg = new SchemeRegistry();

schReg.register(new Scheme("http",

PlainSocketFactory.getSocketFactory(), 80));

schReg.register(new Scheme("https",

SSLSocketFactory.getSocketFactory(), 443));

ClientConnectionManager conMgr = new

ThreadSafeClientConnManager(params,schReg);

customHttpClient = new DefaultHttpClient(conMgr, params);

}

return customHttpClient;

}

 

public Object clone() throws CloneNotSupportedException {

throw new CloneNotSupportedException();

}

}

10、AsyncTask：如果主線程沒有在5秒內(nèi)處理完某個(gè)事件，將觸發(fā)ANR（應(yīng)用程序未響應(yīng)）條件，影響用戶體驗(yàn)。如果用戶只是希望簡(jiǎn)單計(jì)算，無(wú)需更新用戶界面，則可以使用簡(jiǎn)單的Thread對(duì)象來(lái)從主線程轉(zhuǎn)移一些處理工作，但是此技術(shù)不適用于對(duì)用戶界面施行更新，因?yàn)锳ndroid用戶界面工具包不是線程安全的，所以它應(yīng)該始終只從主線程更新。如果希望從后臺(tái)線程以任何方式更新用戶界面，應(yīng)該認(rèn)真考慮使用AsyncTask。AsyncTask負(fù)責(zé)創(chuàng)建一個(gè)后臺(tái)線程來(lái)完成工作，提供將在主線程上運(yùn)行的回調(diào)函數(shù)來(lái)實(shí)現(xiàn)對(duì)用戶界面元素的訪問(wèn)�；卣{(diào)可在后臺(tái)線程運(yùn)行之前、期間、之后觸發(fā)。

11、

 

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  本文關(guān)鍵詞：精通Android3，由筆耕文化傳播整理發(fā)布。

本文編號(hào)：146788