java - 从 onPostExecute 和 doInBackground 返回 boolean 值

Question

我正在寻找解决我的问题的方法。

我在我的 Activity 中调用 AsyncTask:

login.execute(emailText.getText().toString(), passwordText.getText().toString());

在登录类中，我检查用户是否存在。

public class Login extends AsyncTask<String, Boolean, Void> {

public Login(Application application){
    repository = new Repository(application);
}

@Override
protected Boolean doInBackground(String... body){
    try {
        user = repository.getUser(body[0], body[1]);
        if (user != null)
            return true; //wont work
        else {
            return false;
        }
    }
    catch(Exception e){
        return null;
    }
}

protected void onPostExecute(Long result) {
   //i want to have bool value here that i will see in my activity
}

我的问题是，当条件匹配时，如何从 AsyncTask 获取 bool 值？是否有任何可能的方式来调用这样的方法？

boolean valid = login.execute();

感谢帮助

Answer 1

将 onPostExecute() 参数类型更改为 Boolean，然后告诉谁会对发生的结果感兴趣。

对于最后一部分，您可以拥有一个接口(interface)并让某人(感兴趣的类)实现它。

public class Login extends AsyncTask<String, Boolean, Boolean> {

  private LoginListener listener;

  public Login(Application application, LoginListener listener){
    repository = new Repository(application);
    this.listener = listener;
  }

  @Override
  protected Boolean doInBackground(String... body){
    try {
        user = repository.getUser(body[0], body[1]);
        if (user != null)
            return true; //wont work
        else {
            return false;
        }
    }
    catch(Exception e){
        return null;
    }
  }

  protected void onPostExecute(Boolean result) {
   listener.onLoginPerformed(result)
  }



  public static interface LoginListener{
    public void onLoginPerformed(Boolean result);
  }
}

然后假设您希望 MainActivity 在登录时使用react:

public class MainActivity extends AppCompatActitvity implements LoginListener{
    ....
    // When you create the Login object, in onCreate() for example:
    // new Login(application, this); // this is the activity acting as listener...

    @Override public void onLoginPerformed(Boolean result){
        // do what you want to do with the result in Main Activity
    }

}