Java 什么';实现异步任务的正确方法是什么?静态还是非静态嵌套类?
来自Android示例的“登录”作为非静态内部类实现了Java 什么';实现异步任务的正确方法是什么?静态还是非静态嵌套类?,java,android,asynchronous,android-asynctask,Java,Android,Asynchronous,Android Asynctask,来自Android示例的“登录”作为非静态内部类实现了AsyncTask。然而,根据CommonGuys的说法,这个类应该是静态的,并且对外部活动使用弱引用 那么,实现AsyncTask的正确方法是什么呢?静态还是非静态 实施 从谷歌登录示例 package com.example.asynctaskdemo; import android.animation.Animator; import android.animation.AnimatorListenerAdapter; import
AsyncTask
。然而,根据CommonGuys的说法,这个类应该是静态的,并且对外部活动使用弱引用
那么,实现AsyncTask
的正确方法是什么呢?静态还是非静态
实施从谷歌登录示例
package com.example.asynctaskdemo;
import android.animation.Animator;
import android.animation.AnimatorListenerAdapter;
import android.annotation.TargetApi;
import android.app.Activity;
import android.os.AsyncTask;
import android.os.Build;
import android.os.Bundle;
import android.text.TextUtils;
import android.view.KeyEvent;
import android.view.Menu;
import android.view.View;
import android.view.inputmethod.EditorInfo;
import android.widget.EditText;
import android.widget.TextView;
/**
* Activity which displays a login screen to the user, offering registration as
* well.
*/
public class LoginActivity 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);
// 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, 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);
}
}
}
package com.example.asynctaskdemo;
导入android.animation.Animator;
导入android.animation.AnimatorListenerAdapter;
导入android.annotation.TargetApi;
导入android.app.Activity;
导入android.os.AsyncTask;
导入android.os.Build;
导入android.os.Bundle;
导入android.text.TextUtils;
导入android.view.KeyEvent;
导入android.view.Menu;
导入android.view.view;
导入android.view.inputmethod.EditorInfo;
导入android.widget.EditText;
导入android.widget.TextView;
/**
*向用户显示登录屏幕的活动,提供注册为
*嗯。
*/
公共类LoginActivity扩展了活动{
/**
*包含已知用户名和密码的虚拟身份验证存储。
*TODO:连接到真实身份验证系统后删除。
*/
私有静态最终字符串[]伪_凭据=新字符串[]{”foo@example.com:你好“bar@example.com:世界“};
/**
*用于填充电子邮件字段的默认电子邮件。
*/
public static final String EXTRA_EMAIL=“com.example.android.authenticatordemo.EXTRA.EMAIL”;
/**
*跟踪登录任务,确保我们可以根据请求取消它。
*/
private UserLoginTask mAuthTask=null;
//尝试登录时的电子邮件和密码值。
私有字符串mEmail;
私有字符串mPassword;
//用户界面引用。
私有编辑文本mEmailView;
私有编辑文本mPasswordView;
私有视图mloginfo视图;
私有视图mLoginStatusView;
私有文本视图mLoginStatusMessageView;
@凌驾
创建时受保护的void(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
setContentView(R.layout.activity\u登录);
//设置登录表单。
mEmail=getIntent().getStringExtra(额外电子邮件);
mEmailView=(EditText)findViewById(R.id.email);
mEmailView.setText(mEmail);
mPasswordView=(EditText)findViewById(R.id.password);
mPasswordView.setOnEditorActionListener(新的TextView.OnEditorActionListener(){
@凌驾
公共布尔onEditorAction(TextView TextView、int id、KeyEvent KeyEvent){
if(id==R.id.login | | id==EditorInfo.IME_NULL){
尝试登录();
返回true;
}
返回false;
}
});
mLoginFormView=findviewbyd(R.id.login\u表单);
mLoginStatusView=findviewbyd(R.id.login\u状态);
mLoginStatusMessageView=(TextView)findviewbyd(R.id.login\u status\u message);
findviewbyd(R.id.sign_in_按钮)。setOnClickListener(新视图。OnClickListener(){
@凌驾
公共void onClick(视图){
尝试登录();
}
});
}
@凌驾
公共布尔onCreateOptions菜单(菜单){
super.onCreateOptions菜单(菜单);
getMenuInflater().充气(R.menu.activity\u登录,菜单);
返回true;
}
/**
*尝试登录或注册登录表单指定的帐户。
*如果存在表单错误(无效电子邮件、缺少字段等),则
*出现错误,未进行实际登录尝试。
*/
public void attemptLogin(){
if(mAuthTask!=null){
返回;
}
//重置错误。
mEmailView.setError(null);
mPasswordView.setError(null);
//在尝试登录时存储值。
mEmail=mEmailView.getText().toString();
mPassword=mPasswordView.getText().toString();
布尔取消=假;
视图焦点视图=空;
//检查密码是否有效。
if(TextUtils.isEmpty(mPassword)){
mPasswordView.setError(getString(R.string.error_字段_必填));
focusView=mPasswordView;
取消=真;
}
else if(mPassword.length()<4){
mPasswordView.setError(getString(R.string.error\u密码无效));
focusView=mPasswordView;
取消=真;
}
//检查有效的电子邮件地址。
if(TextUtils.isEmpty(mEmail)){
setError(getString(R.string.error_字段_必填));
focusView=mEmailView;
取消=真;
}
如果(!mEmail.contains(@)),则为else{
mEmailView.setError(getString(R.string.error\u无效的电子邮件));
focusView=mEmailView;
取消=真;
}
如果(取消){
//出现错误;请不要尝试登录并在第一次登录时集中注意力
//表单字段有错误。
focusView.requestFocus();
}
否则{
//显示进度微调器,并启动后台任务以
//执行用户登录尝试。
mLoginStatusMessageView.setText(R.string.login\u progress\u signing\u in);
显示进度(真实);
mAuthTask=新用户登录任务();
mAuthTask.execute((Void)null);
}
}
/**
*显示进度UI并隐藏登录表单。
*/
@TargetApi(构建版本代码蜂窝MR2)
私有void showProgress(最终布尔值显示){
//在蜂巢MR2上,我们有ViewPropertyAnimator API,它允许
//对于非常简单的动画。如果可用,请使用这些API淡入
//进度微调器。
如果(Build.VERSION.SDK\u INT>=Build.VERSION\u code_
non-static:
@Override
protected void onProgressUpdate(String... values) {
runOnUiThread(() -> {
TextView tv_results = findViewById(R.id.tv_results);
tv_results.append(values[0] + "\n");
});
}
static:
@Override
protected void onProgressUpdate(String... values) {
OnTaskStringUpdatedListener.OnTaskStringUpdated(task, values[0]);
}