android - EditText 的 TextWatcher 验证器

Question

我正在做一个登录 Activity，它基本上有一个 EditText 和两个 Buttons。它看起来像这样:

http://img249.imageshack.us/img249/9108/loginm.png http://img249.imageshack.us/img249/9108/loginm.png

EditText 有一个 TextWatcher，它通过点击网络服务的 AsyncTask 验证用户。

代码:

public class Login extends Activity {

    private EditText mUserNameET;
    private Drawable mCorrect;
    private Drawable mIncorrect;
    private ProgressBar mProgressBar;
    private MyApp mApp;

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

        mApp = (MyApp) getApplication();
        mUserNameET = (EditText) findViewById(R.id.user_name_et);
        mUserNameET.addTextChangedListener(new LoginValidator());

        mCorrect = getResources().getDrawable(R.drawable.correct);
        mIncorrect = getResources().getDrawable(R.drawable.incorrect);
        mProgressBar = new ProgressBar(this);
    }

    private class LoginValidator implements TextWatcher {

        private ValidateUserAsyncTask validator = new ValidateUserAsyncTask();

        @Override
        public void afterTextChanged(Editable s) {

            String value = s.toString();

            if ( value.length() == 0 )
                return;

            /* If it's running, cancel it. */
            /* Issue #2 */
            if ( AsyncTask.Status.RUNNING == validator.getStatus() ) {
                validator.cancel(true);
                validator = new ValidateUserAsyncTask();
            } else if ( AsyncTask.Status.FINISHED == validator.getStatus() ) {
                validator = new ValidateUserAsyncTask();
            }

            validator.execute(value);
            /* Issue #1 */
            mUserNameET.setCompoundDrawables(null, null, mProgressBar.getProgressDrawable(), null);
        }

        @Override
        public void beforeTextChanged(CharSequence s, int start, int count,
                int after) {
        }

        @Override
        public void onTextChanged(CharSequence s, int start, int before,
                int count) {
        }
    }

    class ValidateUserAsyncTask extends AsyncTask<String, Void, Boolean> {

        @Override
        protected void onPostExecute(Boolean result) {
            super.onPostExecute(result);

            if ( result ) {
                mUserNameET.setCompoundDrawablesWithIntrinsicBounds(null, null, mCorrect, null);
            } else {
                mUserNameET.setCompoundDrawablesWithIntrinsicBounds(null, null, mIncorrect, null);
            }
        }

        @Override
        protected Boolean doInBackground(String... params) {
            return mApp.validateUser(params[0]);
        }
    }
}

我的问题:

当 AsyncTask 工作时，我想在 EditText 中显示 ProgressBar。我尝试使用:

mUserNameET.setCompoundDrawables(null, null, mProgressBar.getProgressDrawable(), null);

但它不起作用。

我也有点担心创建 AsyncTask 的新实例。我在泄漏内存吗？

Answer 1

While the AsyncTask is working I want to show a ProgressBar inside the EditText

尝试创建一个代表进度指示器的 AnimationDrawable，并将其与 setCompoundDrawables() 一起使用。

And I am also a bit worried about creating new instances of the AsyncTask. Am I leaking memory?

嗯，您不能重用 AsyncTask 实例——它们是一次性的。请记住，AsyncTask 使用线程池，因此您可能同时执行多个 AsyncTasks，这可能与您的想法不符。我会考虑等到没有输入，比如 1 秒钟，然后再执行 Web 服务。