java - AsyncTask 进程

Question

我正在创建一个应用程序，当您使用用户名和密码登录时，它会从服务器请求信息。服务器的请求需要时间（15-20 秒），同时我想用几个词显示一个旋转条。但是我尝试了很多不同的AsyncTask课程，但我无法让它发挥作用。它可以获取信息，但会冻结屏幕直到响应。现在我只有一个新线程实现runnable. 我不确定我需要从代码中的哪个位置调用AsyncTask.

onClick触发attemptLogin()函数：

    public void onClick(View view) {
        attemptLogin();
    }

在attemptLogin()功能上：

// more code
showProgress(true);
new Thread(new GetServerResponseRunnable()).start();
while (wait) {}
// more code

Runnable 是：

public class GetServerResponseRunnable implements Runnable {
    @Override
    public void run() {
        response = getInfo.getTours(mUsername, mPassword);
        wait = false;   
    }       

}  

如您所见，它从不同的类中调用另一个函数。这是功能：

public String getTours(String username, String password) {
    String req = "GETALLDATA";
    String retStr = "";
    try {
        url = getURL(req, username, password);
        sendOutputLine(url, "");
        retStr = getReturnString();
        Log.d(LoginActivity.DEBUG_TAG, "getTours() return: " + retStr);
    } catch (Exception e) {
        Log.d(LoginActivity.DEBUG_TAG, "programm bommed client: " + e.getMessage());
    }
    return retStr;
}   

我需要帮助，请。主要是我想做的是：

    response = getInfo.getTours(mUsername, mPassword);
    wait = false;

同时显示旋转杆。

谢谢

---

更新：2013 年 2 月 13 日

我使用了这段代码，但我得到了一个

02-13 09:07:16.142: E/AndroidRuntime(1046): java.lang.NullPointerException

在行中：

this.dialog.setMessage(getResources().getString(R.string.login_progress_signing_in));

知道为什么吗？

public class LoginTask extends AsyncTask<Object, Void, String> {

    public Context context;
    public ProgressDialog dialog;


    public void BaseTask(Context context) {
        this.context = context;
        this.dialog = new ProgressDialog(context);
    }

    @Override
    protected void onPreExecute() {
        this.dialog.setMessage(getResources().getString(R.string.login_progress_signing_in));
        this.dialog.show();

    }

    @Override
    protected String doInBackground(Object... objects) {
        String name = (String) objects[0];
        String password = (String) objects[1];
        String response = getInfo.getTours(name , password );
        return response;
    }

    @Override
    protected void onPostExecute(String response) {
        if (dialog != null && dialog.isShowing())
            dialog.dismiss();

        LoginActivity.response = response; 

        // process response as you need
    }
} 

Answer 1

我想你需要这样的东西

public class LoginTask extends AsyncTask<Object, Void, String> {

    public Context context;
    public ProgressDialog dialog;


    public BaseTask(Context context) {
        this.context = context;
        this.dialog = new ProgressDialog(context);
    }

    @Override
    protected void onPreExecute() {
        this.dialog.setMessage(context.getResources().getString(R.string.loading));
        this.dialog.show();

    }

    @Override
    protected String doInBackground(Object... objects) {
        String name = (String) objects[0];
        String password = (String) objects[1];
        String response = getInfo.getTours(name , password );
        return response;
    }

    @Override
    protected void onPostExecute(String response) {
        if (dialog != null && dialog.isShowing())
            dialog.dismiss();

        // process response as you need
    }
}

称之为任务

public void onClick(View view) {
    new LoginTask(YourActivity.this).execute(name, password);
}

Answer 2

您的 AsyncTask 可能看起来像这样：

 private class DownloadFilesTask extends AsyncTask<Login, Void, Tours> {
     protected void onPreExecute(){
        //show the dialog here
     }

     protected Long doInBackground(URL... urls) {
         Tours response = getInfo.getTours(Login.mUsername, Login.mPassword);
         return response;
     }


     protected void onPostExecute(Long result) {
         //hide the dialog here
     }
 }

我对您的项目了解得不够多，无法将其纳入其中，您必须对其进行一些自定义，但整体“方式”将与此类似。

Answer 3

尝试实现android登录活动。在你的 ADT 下创建新的活动选择：登录活动这将为你生成以下模板代码：

/**
 * Activity which displays a login screen to the user, offering registration as
 * well.
 */
public class LoginActivityTest extends Activity {
    /**
     * A dummy authentication store containing known user names and passwords.
     * TODO: remove after connecting to a real authentication system.
     */
    private static final String[] DUMMY_CREDENTIALS = new String[] {
            "foo@example.com:hello", "bar@example.com:world" };

    /**

         * The default email to populate the email field with.
         */
        public static final String EXTRA_EMAIL = "com.example.android.authenticatordemo.extra.EMAIL";

        /**
         * Keep track of the login task to ensure we can cancel it if requested.
         */
        private UserLoginTask mAuthTask = null;

        // Values for email and password at the time of the login attempt.
        private String mEmail;
        private String mPassword;

        // UI references.
        private EditText mEmailView;
        private EditText mPasswordView;
        private View mLoginFormView;
        private View mLoginStatusView;
        private TextView mLoginStatusMessageView;

        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);

            setContentView(R.layout.activity_login_activity_test);

            // Set up the login form.
            mEmail = getIntent().getStringExtra(EXTRA_EMAIL);
            mEmailView = (EditText) findViewById(R.id.email);
            mEmailView.setText(mEmail);

            mPasswordView = (EditText) findViewById(R.id.password);
            mPasswordView
                    .setOnEditorActionListener(new TextView.OnEditorActionListener() {
                        @Override
                        public boolean onEditorAction(TextView textView, int id,
                                KeyEvent keyEvent) {
                            if (id == R.id.login || id == EditorInfo.IME_NULL) {
                                attemptLogin();
                                return true;
                            }
                            return false;
                        }
                    });

            mLoginFormView = findViewById(R.id.login_form);
            mLoginStatusView = findViewById(R.id.login_status);
            mLoginStatusMessageView = (TextView) findViewById(R.id.login_status_message);

            findViewById(R.id.sign_in_button).setOnClickListener(
                    new View.OnClickListener() {
                        @Override
                        public void onClick(View view) {
                            attemptLogin();
                        }
                    });
        }

        @Override
        public boolean onCreateOptionsMenu(Menu menu) {
            super.onCreateOptionsMenu(menu);
            getMenuInflater().inflate(R.menu.activity_login_activity_test, menu);
            return true;
        }

        /**
         * Attempts to sign in or register the account specified by the login form.
         * If there are form errors (invalid email, missing fields, etc.), the
         * errors are presented and no actual login attempt is made.
         */
        public void attemptLogin() {
            if (mAuthTask != null) {
                return;
            }

            // Reset errors.
            mEmailView.setError(null);
            mPasswordView.setError(null);

            // Store values at the time of the login attempt.
            mEmail = mEmailView.getText().toString();
            mPassword = mPasswordView.getText().toString();

            boolean cancel = false;
            View focusView = null;

            // Check for a valid password.
            if (TextUtils.isEmpty(mPassword)) {
                mPasswordView.setError(getString(R.string.error_field_required));
                focusView = mPasswordView;
                cancel = true;
            } else if (mPassword.length() < 4) {
                mPasswordView.setError(getString(R.string.error_invalid_password));
                focusView = mPasswordView;
                cancel = true;
            }

            // Check for a valid email address.
            if (TextUtils.isEmpty(mEmail)) {
                mEmailView.setError(getString(R.string.error_field_required));
                focusView = mEmailView;
                cancel = true;
            } else if (!mEmail.contains("@")) {
                mEmailView.setError(getString(R.string.error_invalid_email));
                focusView = mEmailView;
                cancel = true;
            }

            if (cancel) {
                // There was an error; don't attempt login and focus the first
                // form field with an error.
                focusView.requestFocus();
            } else {
                // Show a progress spinner, and kick off a background task to
                // perform the user login attempt.
                mLoginStatusMessageView.setText(R.string.login_progress_signing_in);
                showProgress(true);
                mAuthTask = new UserLoginTask();
                mAuthTask.execute((Void) null);
            }
        }

        /**
         * Shows the progress UI and hides the login form.
         */
        @TargetApi(Build.VERSION_CODES.HONEYCOMB_MR2)
        private void showProgress(final boolean show) {
            // On Honeycomb MR2 we have the ViewPropertyAnimator APIs, which allow
            // for very easy animations. If available, use these APIs to fade-in
            // the progress spinner.
            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB_MR2) {
                int shortAnimTime = getResources().getInteger(
                        android.R.integer.config_shortAnimTime);

                mLoginStatusView.setVisibility(View.VISIBLE);
                mLoginStatusView.animate().setDuration(shortAnimTime)
                        .alpha(show ? 1 : 0)
                        .setListener(new AnimatorListenerAdapter() {
                            @Override
                            public void onAnimationEnd(Animator animation) {
                                mLoginStatusView.setVisibility(show ? View.VISIBLE
                                        : View.GONE);
                            }
                        });

                mLoginFormView.setVisibility(View.VISIBLE);
                mLoginFormView.animate().setDuration(shortAnimTime)
                        .alpha(show ? 0 : 1)
                        .setListener(new AnimatorListenerAdapter() {
                            @Override
                            public void onAnimationEnd(Animator animation) {
                                mLoginFormView.setVisibility(show ? View.GONE
                                        : View.VISIBLE);
                            }
                        });
            } else {
                // The ViewPropertyAnimator APIs are not available, so simply show
                // and hide the relevant UI components.
                mLoginStatusView.setVisibility(show ? View.VISIBLE : View.GONE);
                mLoginFormView.setVisibility(show ? View.GONE : View.VISIBLE);
            }
        }

        /**
         * Represents an asynchronous login/registration task used to authenticate
         * the user.
         */
        public class UserLoginTask extends AsyncTask<Void, Void, Boolean> {
            @Override
            protected Boolean doInBackground(Void... params) {
                // TODO: attempt authentication against a network service.

                try {
                    // Simulate network access.
                    Thread.sleep(2000);
                } catch (InterruptedException e) {
                    return false;
                }

                for (String credential : DUMMY_CREDENTIALS) {
                    String[] pieces = credential.split(":");
                    if (pieces[0].equals(mEmail)) {
                        // Account exists, return true if the password matches.
                        return pieces[1].equals(mPassword);
                    }
                }

                // TODO: register the new account here.
                return true;
            }

            @Override
            protected void onPostExecute(final Boolean success) {
                mAuthTask = null;
                showProgress(false);

                if (success) {
                    finish();
                } else {
                    mPasswordView
                            .setError(getString(R.string.error_incorrect_password));
                    mPasswordView.requestFocus();
                }
            }

            @Override
            protected void onCancelled() {
                mAuthTask = null;
                showProgress(false);
            }
        }
    }

这UserLoginTask是您要进行身份验证的地方。这将允许您在尝试登录时显示微调器。“onPostExecute”将是您在验证后移至下一个活动的地方，或者返回登录屏幕并为用户显示一条消息，例如密码无效。

请注意，该模板包含 dummy_credentials，如果您使用服务器进行身份验证则不需要这些，并且它带有电子邮件和密码 textEdits，但您可以将它们更改为您想要的任何内容。

Answer 4

您需要实现一个新的扩展类，AsyncTask在一个名为的函数内完成所有广泛的工作doInBackground，并使用其他一些常用方法（如onProgressUpdate. 在网络上快速搜索“android asynctask tutorial”会产生一些不错的结果供您学习。