android错误之android.os.NetworkOnMainThreadException

大家好，又见面了，我是全栈君。

在做一个天气预报的widget的时候，参考了一个源代码，但是一直报错，就从里面抠出来获取天气的代码试试看，结果总是报错

就是这个异常，android.os.NetworkOnMainThreadException

代码是这样的：

MainActivity：

public class MainActivity extends Activity {
	
	MyWeather myWeather;
	
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		myWeather = new MyWeather();
		System.out.println(myWeather.getCity());
	}
}

MyWeather：

public class MyWeather {
	public String city;
	public String temp1;
	public String weather1;
	public String img1;
	
	public MyWeather(){
		getWeather();
	}
	
	public void getWeather(){
		
		try {
			URL url = new URL("http://m.weather.com.cn/data/101250101.html");
			InputStream is = url.openStream();
			int len = -1;
			byte[] buffer = new byte[1024];
			ByteArrayOutputStream bos = new ByteArrayOutputStream();
			while ((len = is.read(buffer)) != -1) {
				bos.write(buffer, 0, len);
			}
			String info = bos.toString("utf-8");
			JSONObject dataJson = new JSONObject(info);
			JSONObject json = dataJson.getJSONObject("weatherinfo");
			city = json.getString("city");
			temp1 = json.getString("temp1");
			weather1 = json.getString("weather1");
			img1 = json.getString("img1");
			bos.close();
			is.close();
			
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}catch (JSONException e) {
			// TODO: handle exception
		}
	}
	public String getCity() {
		return city;
	}

	public void setCity(String city) {
		this.city = city;
	}

	public String getTemp1() {
		return temp1;
	}

	public void setTemp1(String temp1) {
		this.temp1 = temp1;
	}

	public String getWeather1() {
		return weather1;
	}

	public void setWeather1(String weather1) {
		this.weather1 = weather1;
	}

	public String getImg1() {
		return img1;
	}

	public void setImg1(String img1) {
		this.img1 = img1;
	}

}

经过查阅资料，大体错误应该是这样的，主要是说主线程访问网络时出的异常。

 Android在4.0之前的版本 支持在主线程中访问网络，但是在4.0以后对这部分程序进行了优化，也就是说访问网络的代码不能写在主线程中了。

于是把MainActivity的代码改成如下就可以了，在新开的线程中读取天气，用handler异步加载：

public class MainActivity extends Activity {

	MyWeather myWeather;

	private Handler handler = new Handler() {
		public void handleMessage(Message msg) {
			switch (msg.what) {
			case 0:
				System.out.println("jason.com" + myWeather.getCity());
				break;
			}
		};
	};

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		new Thread() {
			@Override
			public void run() {
				// TODO Auto-generated method stub
				super.run();
				myWeather = new MyWeather();
				Message msg = handler.obtainMessage();
				msg.what = 0;
				handler.sendMessage(msg);
			}
		}.start();
	}
}

作者：jason0539

微博：http://weibo.com/2553717707

博客：http://blog.csdn.net/jason0539（转载请说明出处）