判断网络是否连接

/**
* 检测网络是否可用
*
*/
public boolean isNetworkConnected() {
ConnectivityManager cm = (ConnectivityManager) getSystemService(MainActivity.this.CONNECTIVITY_SERVICE);
NetworkInfo ni = cm.getActiveNetworkInfo();
return ni != null && ni.isConnectedOrConnecting();
}

boolean connected = isNetworkConnected();
if(connected){
Toast.makeText(this, "网络已连接", 0).show();
}else{
Toast.makeText(this, "网络未连接", 0).show();
}