调试时 onPostExecute() 与 doInBackground() 无关

Question

我在 AsyncTask class 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; }

实现我的接口以从 onPostExecute():

捕获结果

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

现在，我在代码中触发的AsyncTask：

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，为什么当我第一次点击按钮时，func return Boolean.TRUE 但在 SignupActivity signupValid 变量是 false （注册表单没有退出，但用户被添加到数据库），但是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）但是 signupValid 更改为 true 并且注册表单通过了？我需要单击 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，但现在我得到 Toast 甚至在 AsyncTask 之前我的表单无效工作。而且，即使从 doInBackground() 我得到 TRUE，第一次点击 signupValid 也是错误的，第二次点击 AsyncTask return FALSE 但是 signupValid 更改为 true

我的 UserDAO:

@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

如果我对问题的理解正确 - 存在竞争条件，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);
            }
        }
    }
});

虽然这些行：

 // 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您的异步任务完成之前执行的）

澄清一下：

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

}

调试时 onPostExecute() 与 doInBackground() 无关

onPostExecute() not related to doInBackground() while debugging

java

android

android-asynctask

android-room

android-jetpack