调试时，java onPostExecute（）与doInBackground（）无关

Question

我在AsyncTask类中的onPostExecute()方法有问题

我有一个SignupActivity：

public class SignupActivity extends AppCompatActivity implements SignupListener {

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.signup_activity);

    //new task, i pass context and interface to it
    signup = new Signup(getApplicationContext(), this);

    signupButon.setOnClickListener(new View.OnClickListener(){
        @Override
        public void onClick(View v){
            if(validate()) {
                try {
                    //new task every click
                    Signup newSignup = new Signup(signup);
                    //here start AsyncTask
                    newSignup.execute(name, email, password).get();
                } catch (Exception e) {
                    Toast.makeText(ERROR);
                }
                // if sign up succes, == true;
                if(signupValid) {
                    Toast.makeText(SUCCES);
                    finish();
                } else {
                    Toast.makeText(ERROR);
                }
            }
        }
    });
}

// my own interface for getting result as bool from onPostExecute
@Override
public void onSignupPerformed(Boolean result){ this.signupValid = result; }

实现从onPostExecute()捕获结果的接口：

public interface SignupListener{
    void onSignupPerformed(Boolean result);
}

现在，AsyncTask我在代码中触发：

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

public Signup(Context context, SignupListener listener){
    db = ApplicationDatabase.getDatabase(context);
    this.context = context;
    this.listener = listener;
}

public Signup(Signup signup){
    //constructor to make new task based on first task
    db = signup.db;
    context = signup.context;
    listener = signup.listener;
}

protected Boolean doInBackground(String... body){
    try {
            user = db.userDao().getUser(body[0], body[1], body[2]);
            if (user == null) {
                // user is null, so we can add new one to DB
                db.userDao().insertUser(new User(body[0], body[1], body[2]));
                return Boolean.TRUE; //signup go good, return true
            } else {
                return Boolean.FALSE; //signup go bad, return false
            }
    } catch(Exception e) { }
        return null;
}

protected void onPostExecute(Boolean result) {
    //catching result from doInBackground
    listener.onSignupPerformed(result);
}

我的问题是，为什么当我第一次单击按钮时，func返回Boolean.TRUE，但在SignupActivity{}中，变量是false（注册表单不退出，但用户被添加到数据库），但当我第二次单击注册按钮时，ofc注册失败（因为我们在几秒钟前创建了新用户），但signupValid更改为true，注册表单通过？我需要点击SignupButton两次才能最终退出表单。感谢您在我的代码中发现错误

编辑：

我用Progress Dialog替换了.get()以阻止UI，但现在我甚至在AsyncTask注册之前就用无效形式得到了Toast。尽管如此，在第一次单击中signupValid是假的，即使从doInBackground()我得到TRUE，在第二次单击中AsyncTask返回FALSE，但是signupValid更改为true

我的用户道：

@Dao
public interface UserDao {
    @Query("SELECT * FROM users WHERE email = :email AND password = :password AND username = :username")
    User getUser(String username, String email, String password);
}

和ApplicationDatabase:

public abstract class ApplicationDatabase extends RoomDatabase {

public abstract UserDao userDao();

public static ApplicationDatabase getDatabase(final Context context){
    if(INSTANCE == null){
        synchronized (ApplicationDatabase.class){
            if(INSTANCE == null){
                INSTANCE = Room.databaseBuilder(context.getApplicationContext(), ApplicationDatabase.class, "database").build();
            }
        }
    }
    return INSTANCE;
}

private static volatile ApplicationDatabase INSTANCE;

Answer 1

如果我正确理解了这个问题，那么有一个竞争条件使得SignupActivity在Signup任务执行完成之前触发toast。因此：

signupButon.setOnClickListener(new View.OnClickListener(){
    @Override
    public void onClick(View v){
        if(validate()) {
            try {
                //new task every click
                Signup newSignup = new Signup(signup);
                //here start AsyncTask
                newSignup.execute(name, email, password).get();
            } catch (Exception e) {
                Toast.makeText(ERROR);
            }
        }
    }
});

而这些线：

 // if sign up succes, == true;
 if(signupValid) {
    Toast.makeText(SUCCES);
    finish();
 } else {
    Toast.makeText(ERROR);
 }

应该是listener的一部分（现在看来，这些行是在异步任务完成之前执行的）

我想澄清一下：

@Override
public void onSignupPerformed(Boolean result)
{ 
     if(result) {
        Toast.makeText(SUCCES);
        finish();
     } else {
        Toast.makeText(ERROR);
     }

}