android 强制2G/3G或WIFI 优先上网

android开发中有时候需要设定程序连接网络优先 2G/3G 或 WIFI，下面片段代码给出设置方法：

	public void setPreferredNetwork(int networkType) {
		ConnectivityManager connMgr = (ConnectivityManager) this.context.getSystemService("connectivity");
		if (networkType == NetworkType.TYPE_MOBILE) {//设为2G/3G网络优先，就算wifi连接到AP，系统仍然通过2G/3G访问网络
			connMgr.setNetworkPreference(0);
		} else if (networkType == NetworkType.TYPE_WIFI) {
			connMgr.setNetworkPreference(1);
		}
		WifiManager wifiMgr = (WifiManager) this.context.getSystemService("wifi");
		wifiMgr.disconnect();
	}