调试时 onPostExecute() 与 doInBackground() 无关

Question

我onPostExecute()在AsyncTask课堂上的方法有问题。

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; }

这实现了我从以下位置捕获结果的接口onPostExecute()：

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;

}

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 signupValid变量中是false（注册表单未退出，但用户已添加到 DB），但是当我第二次单击注册按钮时，ofc 注册失败（因为我们创建了新用户几秒钟前）但signupValid更改为true并通过注册表单？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

Answer 1

如果我正确理解了这个问题 - 有一个竞争条件使得在任务SignupActivity执行完成之前触发 toast Signup。所以：signupButon.setOnClickListener(new View.OnClickListener(){&nbsp; &nbsp; @Override&nbsp; &nbsp; public void onClick(View v){&nbsp; &nbsp; &nbsp; &nbsp; if(validate()) {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; try {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; //new task every click&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; Signup newSignup = new Signup(signup);&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; //here start AsyncTask&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; newSignup.execute(name, email, password).get();&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; } catch (Exception e) {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; Toast.makeText(ERROR);&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; }&nbsp; &nbsp; &nbsp; &nbsp; }&nbsp; &nbsp; }});虽然这些行：&nbsp;// if sign up succes, == true;&nbsp;if(signupValid) {&nbsp; &nbsp; Toast.makeText(SUCCES);&nbsp; &nbsp; finish();&nbsp;} else {&nbsp; &nbsp; Toast.makeText(ERROR);&nbsp;}应该是其中的一部分listener（现在看来这些行是在完成异步任务之前执行的）为了澄清我自己：@Overridepublic void onSignupPerformed(Boolean result){&nbsp;&nbsp; &nbsp; &nbsp;if(result) {&nbsp; &nbsp; &nbsp; &nbsp; Toast.makeText(SUCCES);&nbsp; &nbsp; &nbsp; &nbsp; finish();&nbsp; &nbsp; &nbsp;} else {&nbsp; &nbsp; &nbsp; &nbsp; Toast.makeText(ERROR);&nbsp; &nbsp; &nbsp;}}