Question

我正在创建我的应用的用户注册部分。我正在使用AsyncTask类在一个单独的线程上处理这项工作。我在一个单独的类文件中有我的AsyncTask类。此

public class CreateAccountTask extends AsyncTask<String, Void, String>{

private ProgressDialog mpDialog;
private CreateAccountTask task; 
private Context context;
private Activity activity;
private CreateAccount createAccount;
private AsyncTaskListener asyncTaskListener;


public CreateAccountTask(Activity activity, AsyncTaskListener asyncTaskListener){

    this.activity = activity;
    this.asyncTaskListener = asyncTaskListener;
}


@Override
    protected void onPreExecute() {
        // TODO Auto-generated method stub
        super.onPreExecute();

        mpDialog = new ProgressDialog(activity);

        //mpDialog.setTitle("Creating Account");
        mpDialog.setMessage("Please wait.");
        mpDialog.setCancelable(false);
        mpDialog.setIndeterminate(false);
        mpDialog.setButton(DialogInterface.BUTTON_NEGATIVE, "CANCEL", new DialogInterface.OnClickListener() {

            @Override
            public void onClick(DialogInterface arg0, int arg1) {
                // TODO Auto-generated method stub
                //task.cancel(true);
                mpDialog.dismiss();

            }
        });

        mpDialog.show();

    }


@Override
protected String doInBackground(String... arg0) {
    // TODO Auto-generated method stub

    String fphoneNo = arg0[1];
    String fpassword = arg0[0];

    // create instance of the parseUser Class
    ParseUser newUser = new ParseUser();
    newUser.setUsername(fphoneNo);
    newUser.setPassword(fpassword);

    // here Check if progress dialog has been cancelled

    if (!isCancelled()){

    // if dialog has not been cancelled create the new user here
    newUser.signUpInBackground(new SignUpCallback() {

        @Override
        public void done(ParseException e) {

                  // Something went wrong Sorry!

            if(e != null ){


                if(!isCancelled()){
                mpDialog.dismiss();

                String errorMessage = e.getMessage().toString();

                ErrorHappened(errorMessage);

                }

                else{

                    String errorMessage = "Registration Cancelled!";
                    ErrorHappened(errorMessage);

                }

            }

            // No Problems 
            else {
                if (!isCancelled()) {

                    // Wait for five seconds before starting the activity
                    //verifyingUser();

                }
                else {
                    String errorMessage = "Registration Cancelled2!";
                    ErrorHappened(errorMessage);

                    //Delete user in background
                    ParseUser currentUser = ParseUser.getCurrentUser();
                    if (currentUser != null) {
                        currentUser.deleteInBackground();
                    }

                }
            }   

            }

                    });

    }

    return null;
}

@Override
protected void onPostExecute(String result) {
    // TODO Auto-generated method stub
    super.onPostExecute(result);
    asyncTaskListener.onTaskComplete(result);
}

private void ErrorHappened(String errorMessage) {

    Crouton CreateMagic = Crouton.makeText(createAccount, errorMessage, CroutonClass.ALERT);
    CreateMagic.setConfiguration(CroutonClass.configure);
    CreateMagic.show();


}





}

在我的onPreExecute方法中，我启动了一个progressDialog，它在执行后台任务时显示。在我的doInBackground方法中，我获得了用户在主Activity中提供的用户名和密码，并注册了用户。这是我的问题开始的地方，如果在用户注册期间发生错误，我想使用Crouton（冷却器版本的吐司）通知用户此错误。但是当应用程序到达用crouton显示错误时崩溃了。

我的问题是：

如何在我的活动中显示错误消息？

这是我的活动：

public class CreateAccount extends ActionBarActivity implements AsyncTaskListener {



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


    mPassWord = (EditText) findViewById(R.id.password);
    mcreateAccount = (Button) findViewById(R.id.createAcct);
    mPhoneNumber = (EditText) findViewById(R.id.Phone_Number);



    // create account Method
    createAccount();    

    }//end of on create.


    public void createAccount() {

    mcreateAccount.setOnClickListener(new OnClickListener() {
        @Override
        public void onClick(View arg0) {


                CreateAccountTask newTask = new CreateAccountTask(CreateAccount.this, new CreateAccount());
                newTask.execute(passwordString, fpartphoneNo);



            });

}






private void verifyingUser() {


}

private void shitHappened(String errorMessage) {
    // TODO Auto-generated method stub


    Crouton CreateMagic = Crouton.makeText(this, errorMessage, CroutonClass.ALERT);
    CreateMagic.setConfiguration(CroutonClass.configure);
    CreateMagic.show();


}


@Override
public void onBackPressed() {
    // TODO Auto-generated method stub

    Crouton.cancelAllCroutons();
    super.onBackPressed();
}








@Override
public void onTaskComplete(String result) {
    // TODO Auto-generated method stub



}

}

Answer 1

只允许来自UIThread的通知和任何其他UI操作。如果您查看AsyncTask的文档，doInBackground()会在其自己的主题上运行，而onPreExecute()，onPostExecute()和onCancelled()会在UIThread上运行。

在您的情况下，您应该使用protected void onCancelled(String result)作为通知。它在UIThread上运行，可帮助您区分成功和不成功的操作。要使用此功能，请致电cancel()并检查操作是否已取消doInBackground()。

然后将执行

onCancelled()而不是onPostExecute()

在您的特殊情况下，它可能是上下文的问题，因为您将CreateAccount.this存储在activity的{{1}}中的构造函数中，但您正在使用{{1 }}。尝试将其更改为以下内容：

CreateAccountTask

Answer 2

使用runOnUiThread如下...

@Override
protected void onPreExecute() {
    // TODO Auto-generated method stub
    super.onPreExecute();

    runOnUiThread(new Runnable() {
        @Override
        public void run() {

            mpDialog = new ProgressDialog(activity);

            //mpDialog.setTitle("Creating Account");
            mpDialog.setMessage("Please wait.");
            mpDialog.setCancelable(false);
            mpDialog.setIndeterminate(false);
            mpDialog.setButton(DialogInterface.BUTTON_NEGATIVE, "CANCEL", new DialogInterface.OnClickListener() {

                @Override
                public void onClick(DialogInterface arg0, int arg1) {
                    // TODO Auto-generated method stub
                    //task.cancel(true);
                    mpDialog.dismiss();

                }
            });

            mpDialog.show();

     }

}

在单独的公共asyncTask类的活动中显示错误消息

2 个答案: