Android手機判斷網絡是否可用

ConnectivityManager cm = (ConnectivityManager) this.getSystemService(Context.CONNECTIVITY_SERVICE);
        NetworkInfo activeNetworkInfo = cm.getActiveNetworkInfo();
        if (activeNetworkInfo == null) {
            Toast.makeText(this, "沒有網絡", Toast.LENGTH_SHORT).show();
        } else {
            int type = activeNetworkInfo.getType();
            if (type == cm.TYPE_WIFI) {
                if (activeNetworkInfo.isAvailable()){
                    Toast.makeText(this, "wifi可用", Toast.LENGTH_SHORT).show();
                }else {
                    Toast.makeText(this, "wifi不可用", Toast.LENGTH_SHORT).show();
                }
            } else if (type == cm.TYPE_MOBILE) {
                if (activeNetworkInfo.getExtraInfo().toLowerCase().equals("cmnet")) {
                    if (activeNetworkInfo.isAvailable()){
                        Toast.makeText(this, "net網絡可用", Toast.LENGTH_SHORT).show();
                    }else {
                        Toast.makeText(this, "net網絡不可用", Toast.LENGTH_SHORT).show();
                    }
                } else {
                    if (activeNetworkInfo.isAvailable()){
                        Toast.makeText(this, "wap網絡網絡可用", Toast.LENGTH_SHORT).show();
                    }else {
                        Toast.makeText(this, "wap網絡網絡不可用", Toast.LENGTH_SHORT).show();
                    }
                }
            }
        }