Android 判断当前设备是否联网

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

ConnectivityManager connectivityManager=(ConnectivityManager) getApplication().getSystemService(Context.CONNECTIVITY_SERVICE);

NetworkInfo info=connectivityManager.getActiveNetworkInfo();
        if (info==null) {
            Toast.makeText(this, "false", Toast.LENGTH_LONG).show();
        }else {
            Toast.makeText(this, "true", Toast.LENGTH_LONG).show();
        }