下面的部分内容来源于《Unlocking Android》一书：

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要了解HTTPClient，我们先看一下如何使用核心类来执行HTTP GET和POST方法请求，此处我们结合使用Apache的ResonseHandler和Android的Handler，在与用户界面不同的线程中发起网络请求。

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// new a Handler to receive the response by HTTP request.
private final Handler mHandler = new Handler() {
	public void handleMessage(Message msg) {
		mPrgressDialog.dismiss();
		String result = msg.getData().getString("RESPONSE");
		mOutput.setText(result);
	};
};

@Override
public void onCreate(Bundle savedInstanceState) {
	super.onCreate(savedInstanceState);
	setContentView(R.layout.main);
	mButton = (Button) findViewById(R.id.btn);
	mButton.setOnClickListener(new OnClickListener() {
		public void onClick(View v) {
			mOutput.setText("");
			performRequest(url);
		}
	});
	mOutput = (TextView) findViewById(R.id.output);
}

// perform HTTP request with HttpRequestHelper asynchronously.
private void performRequest(final String url) {
	final ResponseHandler<String> responseHandler = HttpRequestHelper
			.getResponseHandlerInstance(mHandler);
	// show a ProgressDialog to represent that it is woring now, and it
	// will dismiss after receiving response.
	mPrgressDialog = ProgressDialog.show(this, "working...",
			"performing HTTP request");
	new Thread() {
		public void run() {
			HttpRequestHelper helper = new HttpRequestHelper(
					responseHandler);
			// use GET method
			helper.performGet(url, null, null, null);
		};
	}.start();
}

/**
 * Helper for HTTP request via GET or POST method.
 */
public final class HttpRequestHelper {

	private static final int POST_TYPE = 1;
	private static final int GET_TYPE = 2;
	public static final String CONTENT_TYPE = "Content-Type";
	public static final String MIME_FORM_ENCODED = "application/x-www-form-urlencoded";
	public static final String MIME_TEXT_PLAIN = "text/plain";
	private final ResponseHandler<String> mResponseHandler;

	public HttpRequestHelper(ResponseHandler<String> responseHandler) {
		mResponseHandler = responseHandler;
	}

	public void performGet(String url, String user, String pwd,
			final Map<String, String> addtionalHeaders) {
		performRequest(null, url, user, pwd, addtionalHeaders, null, GET_TYPE);
	}

	public void performPost(String contentType, String url, String user,
			String pwd, Map<String, String> addtionalHeaders,
			Map<String, String> params) {
		performRequest(contentType, url, user, pwd, addtionalHeaders, params,
				POST_TYPE);
	}

	public void performPost(String url, String user, String pwd,
			Map<String, String> addtionalHeaders, Map<String, String> params) {
		performRequest(MIME_FORM_ENCODED, url, user, pwd, addtionalHeaders,
				params, POST_TYPE);
	}

	private void performRequest(String contentType, String url, String user,
			String pwd, Map<String, String> headers,
			Map<String, String> params, int requestType) {
		DefaultHttpClient client = new DefaultHttpClient();
		if (user != null && pwd != null) {
			client.getCredentialsProvider().setCredentials(AuthScope.ANY,
					new UsernamePasswordCredentials(user, pwd));
		}

		final Map<String, String> sendHeaders = new HashMap<String, String>();
		if (headers != null && !headers.isEmpty()) {
			sendHeaders.putAll(headers);
		}
		if (POST_TYPE == requestType) {
			sendHeaders.put(CONTENT_TYPE, contentType);
		}
		if (!sendHeaders.isEmpty()) {
			client.addRequestInterceptor(new HttpRequestInterceptor() {

				public void process(HttpRequest request, HttpContext context)
						throws HttpException, IOException {
					for (String key : sendHeaders.keySet()) {
						if (!request.containsHeader(key)) {
							request.addHeader(key, sendHeaders.get(key));
						}
					}
				}
			});
		}

		if (POST_TYPE == requestType) {
			HttpPost post = new HttpPost(url);
			List<NameValueP