<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context=".MainActivity" >

    <LinearLayout 
        android:layout_width="match_parent"
        android:layout_height="wrap_content" 
        android:orientation="horizontal" >

		<TextView
		    android:layout_width="wrap_content"
		    android:layout_height="wrap_content"
		    android:layout_weight="1"
		    android:gravity="center"
		    android:text="城市："
		    android:textSize="23sp" />

		<EditText 
            android:id="@+id/city"
            android:layout_width="wrap_content"
			android:layout_height="wrap_content"
			android:layout_weight="3"
            android:inputType="text" />"
    </LinearLayout>

    <Button
        android:id="@+id/query"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" 
        android:text="查询" 
        android:textSize="23sp" />
    
    <TextView
		android:id="@+id/result"
		android:layout_width="match_parent"
		android:layout_height="match_parent" />
</LinearLayout>

Java源代码文件：MainActivity.java

package com.rainsong.httpclientgetdemo;

import java.io.IOException;
import java.net.URLEncoder;
import java.util.ArrayList;

import org.apache.http.HttpResponse;
import org.apache.http.NameValuePair;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.message.BasicNameValuePair;
import org.apache.http.util.EntityUtils;

import android.os.Bundle;
import android.os.StrictMode;
import android.app.Activity;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends Activity {
    private static final String JUHE_URL_ENVIRONMENT_AIR_PM = 
                                    "http://web.juhe.cn:8080/environment/air/pm";
    private static final String JUHE_APPKEY = "你申请的APPKEY值";
    EditText et_city;
    Button btn_query;
    TextView tv_result;
    
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        // 强制直接在UI线程中进行网络操作
        StrictMode.setThreadPolicy(new StrictMode.ThreadPolicy.Builder()
            .detectDiskReads().detectDiskWrites().detectNetwork()
            .penaltyLog().build());
        StrictMode.setVmPolicy(new StrictMode.VmPolicy.Builder()
            .detectLeakedSqlLiteObjects().detectLeakedClosableObjects()
            .penaltyLog().penaltyDeath().build());

        setContentView(R.layout.activity_main);
        et_city = (EditText)findViewById(R.id.city);
        tv_result = (TextView)findViewById(R.id.result);
        btn_query = (Button)findViewById(R.id.query);
        btn_query.setOnClickListener(new OnClickListener() {
            public void onClick(View view) {
                tv_result.setText("");
                String city;
                city = et_city.getText().toString();
                if (city.length() < 1) {
                    Toast.makeText(MainActivity.this, "请输入城市名",
                            Toast.LENGTH_LONG).show();
                    return;
                }
                ArrayList<NameValuePair> headerList = new ArrayList<NameValuePair>();
                headerList.add(new BasicNameValuePair("Content-Type",
                        "text/html; charset=utf-8"));
                String targetUrl = JUHE_URL_ENVIRONMENT_AIR_PM;
                ArrayList<NameValuePair> paramList = new ArrayList<NameValuePair>();
                paramList.add(new BasicNameValuePair("key", JUHE_APPKEY));
                paramList.add(new BasicNameValuePair("dtype", "json"));
                paramList.add(new BasicNameValuePair("city", city));
                
                for (int i = 0; i < paramList.size(); i++) {
                    NameValuePair nowPair = paramList.get(i);
                    String value = http://www.mamicode.com/nowPair.getValue();>
注：本来不应该直接在UI线程进行网络操作，会阻塞UI，影响用户体验。但为了不引入其他知识点，把焦点聚集在HttpClient网络通信上，在本例中强制直接在UI线程中进行网络操作。在下篇文章中会介绍如何避免直接在UI线程中进行网络操作。

API知识点
public interface
HttpClient

org.apache.http.client.HttpClient

Known Indirect Subclasses
AbstractHttpClient, AndroidHttpClient, DefaultHttpClient

Class Overview
Interface for an HTTP client. HTTP clients encapsulate a smorgasbord of objects required to execute HTTP requests while handling cookies, authentication, connection management, and other features. Thread safety of HTTP clients depends on the implementation and configuration of the specific client.

abstract HttpResponse execute(HttpUriRequest request)
Executes a request using the default context.

public class
DefaultHttpClient
extends AbstractHttpClient

org.apache.http.impl.client.DefaultHttpClient

Class Overview
Default implementation of an HTTP client.

Public Constructor
DefaultHttpClient()
Creates a new HTTP client.

public class
HttpGet
extends HttpRequestBase

Inherited Methods
 From class org.apache.http.client.methods.HttpRequestBase
 From class org.apache.http.message.AbstractHttpMessage
 From class java.lang.Object
 From interface org.apache.http.HttpMessage
 From interface org.apache.http.HttpRequest
 From interface org.apache.http.client.methods.AbortableHttpRequest
 From interface org.apache.http.client.methods.HttpUriRequest

Public Constructors
HttpGet()
HttpGet(URI uri)
HttpGet(String uri)

abstract void addHeader(String name, String value)
Adds a header to this message.

public interface
HttpResponse
implements HttpMessage

org.apache.http.HttpResponse

Class Overview
An HTTP response.

abstract HttpEntity getEntity()
Obtains the message entity of this response, if any.

abstract StatusLine getStatusLine()
Obtains the status line of this response.

public interface
NameValuePair

org.apache.http.NameValuePair

Known Indirect Subclasses
BasicNameValuePair

Class Overview
A simple class encapsulating an attribute/value pair.

Public Methods
abstract String getName()
abstract String getValue()

public class
BasicNameValuePair
extends Object
implements Cloneable NameValuePair

org.apache.http.message.BasicNameValuePair

Public Constructors
BasicNameValuePair(String name, String value)
Default Constructor taking a name and a value.



Android网络编程之使用HttpClient进行Get方式通信