判断网络是否有效

protected boolean isInternetAvailable(Context ctx) {
	try {
		ConnectivityManager cm = (ConnectivityManager) ctx
			.getSystemService(Context.CONNECTIVITY_SERVICE);

		return ((cm.getActiveNetworkInfo() != null)
			&& (cm.getActiveNetworkInfo().isAvailable())
			&& (cm.getActiveNetworkInfo().isConnected()));

	} catch (Exception e) {
		e.printStackTrace()
	}

	return false;
}

需要添加permission

<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />

其实还可以通过Network Information获得连接类型等信息