Android开发WeatherForecast程序

1，使用Googel API
http://www.google.com/ig/api?&weather=beijing

2，使用DOM解析XML

String weather = "";
String url = "http://www.google.com/ig/api?&weather=beijing";
DefaultHttpClient client = new DefaultHttpClient();
HttpUriRequest req = new HttpGet(url);
HttpResponse resp = client.execute(req);
HttpEntity ent = resp.getEntity();
InputStream stream = ent.getContent();
DocumentBuilder b = DocumentBuilderFactory.newInstance().newDocumentBuilder();
Document d = b.parse(new InputSource(stream));
NodeList n = d.getElementsByTagName("forecast_conditions");
for (int i = 0; i < n.getLength(); i++) {
	weather += n.item(i).getChildNodes().item(0).getAttributes().item(0).getNodeValue();
	weather += ", ";
	weather += (Integer.parseInt(n.item(i).getChildNodes().item(1).getAttributes().item(0).getNodeValue()) - 32) * 5 / 9;
	weather += " ~ ";
	weather += (Integer.parseInt(n.item(i).getChildNodes()
								.item(2).getAttributes().item(0).getNodeValue()) - 32) * 5 / 9;
	weather += ", ";
	weather += n.item(i).getChildNodes().item(4).getAttributes().item(0).getNodeValue();
	weather += "\n";
}

3，另起Thread处理Web请求

new Thread() {
	public void run() {
		try {
			// ...
		} catch (Exception e) {
			e.printStackTrace();
		}
	}
}.start();

4，使用Handler传递Thread处理结果到UI主Thread

h = new Handler() {
	public void handleMessage(Message msg) {
		tv.setText((String)msg.obj);
	}
};

new Thread() {
	// ...
	Message msg = h.obtainMessage(1, 1, 1, weather);
	h.sendMessage(msg);
}

5，完整代码

package com.hideto.weatherforecast;

import java.io.InputStream;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.methods.HttpUriRequest;
import org.apache.http.impl.client.DefaultHttpClient;
import org.w3c.dom.Document;
import org.w3c.dom.NodeList;
import org.xml.sax.InputSource;

import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.widget.TextView;

public class WeatherForecast extends Activity {

	public TextView tv;
	public Handler h;

	@Override
	public void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		tv = new TextView(this);
		tv.setText("Loading...");
		setContentView(tv);
		h = new Handler() {
			public void handleMessage(Message msg) {
				tv.setText((String)msg.obj);
			}
		};
		new Thread() {
			public void run() {
				try {
					String weather = "";
					String url = "http://www.google.com/ig/api?&weather=beijing";
					DefaultHttpClient client = new DefaultHttpClient();
					HttpUriRequest req = new HttpGet(url);
					HttpResponse resp = client.execute(req);
					HttpEntity ent = resp.getEntity();
					InputStream stream = ent.getContent();
					DocumentBuilder b = DocumentBuilderFactory.newInstance().newDocumentBuilder();
					Document d = b.parse(new InputSource(stream));
					NodeList n = d.getElementsByTagName("forecast_conditions");
					for (int i = 0; i < n.getLength(); i++) {
						weather += n.item(i).getChildNodes().item(0)
								.getAttributes().item(0).getNodeValue();
						weather += ", ";
						weather += (Integer.parseInt(n.item(i).getChildNodes()
								.item(1).getAttributes().item(0).getNodeValue()) - 32) * 5 / 9;
						weather += " ~ ";
						weather += (Integer.parseInt(n.item(i).getChildNodes()
								.item(2).getAttributes().item(0).getNodeValue()) - 32) * 5 / 9;
						weather += ", ";
						weather += n.item(i).getChildNodes().item(4)
								.getAttributes().item(0).getNodeValue();
						weather += "\n";
					}
					Message msg = h.obtainMessage(1, 1, 1, weather);
					h.sendMessage(msg);
				} catch (Exception e) {
					e.printStackTrace();
				}
			}
		}.start();
	}
}

6，修改AndroidManifest.xml加上INTERNET访问权限

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
      package="com.hideto.weatherforecast"
      android:versionCode="1"
      android:versionName="1.0.0">
    <uses-permission android:name="android.permission.INTERNET"></uses-permission>
    <application android:icon="@drawable/icon" android:label="@string/app_name">
        <activity android:name=".WeatherForecast"
                  android:label="@string/app_name">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>
</manifest>