没法解决paypal paypal-英雄云拓展知识分享

我是编码的新手。我正在尝试将PayPal付款添加到我的利用程序中，并为此找到一个TutorialVideo，但我会遇到一个毛病：

getProofOfPayment 方法没法解决。

你知道为何吗？到至今为止为止，我完成了所有教程中的所有操作，但没有毛病。

这是我的代码：

public class MainActivity extends AppCompatActivity {
TextView m_response;
PayPalConfiguration m_configuration;
String m_paypalClientid;
Intent m_service;
int m_paypalRequestCode = 999;
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
m_response = (TextView) findViewById(R.id.response);
m_configuration = new PayPalConfiguration().environment(PayPalConfiguration.ENVIRONMENT_SANDBOX)
.clientId(m_paypalClientid);
m_service = new Intent(this, PayPalService.class);
m_service.putExtra(PayPalService.EXTRA_PAYPAL_CONFIGURATION, m_configuration);
startService(m_service);
}
void pay (View view){
PayPalPayment payment = new PayPalPayment(new BigDecimal(10), "EUR", "Tes payment for Paypal",
PayPalPayment.PAYMENT_INTENT_SALE);
Intent intent = new Intent(this, PayPalPayment.class);
intent.putExtra(PayPalService.EXTRA_PAYPAL_CONFIGURATION, m_configuration);
intent.putExtra(PaymentActivity.EXTRA_PAYMENT, payment);
startActivityForResult(intent, m_paypalRequestCode);
}
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
if (requestCode == m_paypalRequestCode)
{
if (resultCode == Activity.RESULT_OK)
{
PayPalConfiguration confirmation = data.getParcelableExtra(PaymentActivity.EXTRA_RESULT_CONFIRMATION);
if (confirmation != null)
{
String state = confirmation.getProofOfPayment().getState();
if (state.equals("approved"))
m_response.setText("Payment approved");
else
m_response.setText("Error in the payment");
}
else
m_response.setText("confirmation is null");
}
}
}
}