Android 在上一个任务之前执行后台任务（如何防止）
我在后台发送电子邮件时遇到问题。我试图将文本集作为电子邮件放入EditText中，但我的邮箱中总是出现空值，因为在我在EditText中键入任何内容之前，始终会调用AsyncTask，然后在对话框中按“ok”Android 在上一个任务之前执行后台任务（如何防止）,android,multithreading,asynchronous,android-asynctask,Android,Multithreading,Asynchronous,Android Asynctask,我在后台发送电子邮件时遇到问题。我试图将文本集作为电子邮件放入EditText中，但我的邮箱中总是出现空值，因为在我在EditText中键入任何内容之前，始终会调用AsyncTask，然后在对话框中按“ok” final int partsCount = imageKeeperList.size(); class PhotoSend extends AsyncTask <Void, Void, Void>{
final int partsCount = imageKeeperList.size();
class PhotoSend extends AsyncTask <Void, Void, Void>{
@Override
protected void onPreExecute() {
}
@Override
protected Void doInBackground(Void... voids) {
final String username = "sampleemail@gmail.com";
final String password = "somepassword";
Properties props = new Properties();
props.put("mail.smtp.host", "smtp.gmail.com");
props.put("mail.smtp.socketFactory.port", "465");
props.put("mail.smtp.socketFactory.class", "javax.net.ssl.SSLSocketFactory");
props.put("mail.smtp.auth", "true");
props.put("mail.smtp.port", "465");
Session session = Session.getDefaultInstance(props,
new javax.mail.Authenticator() {
protected PasswordAuthentication getPasswordAuthentication() {
return new PasswordAuthentication(username,password);
}
});
try {
Message message = new MimeMessage(session);
message.setFrom(new InternetAddress("sampleemail@gmail.com"));
message.setRecipients(Message.RecipientType.TO, InternetAddress.parse("targetemail@gmail.pl"));
message.setSubject("Subject of email");
message.setText("Some text.");
Transport.send(message);
Log.d(TAG, "onInput: background");
} catch (MessagingException e) {
throw new RuntimeException(e);
}
return null;
}
@Override
protected void onPostExecute(Void aVoid) {
Toast.makeText(getContext(), "Sent.", Toast.LENGTH_SHORT).show();
Log.d(TAG, "onInput: postExecute");
}
}
new MaterialDialog.Builder(getContext())
.content("Set description")
.inputType(InputType.TYPE_TEXT_FLAG_IME_MULTI_LINE)
.input("short description", "", new MaterialDialog.InputCallback() {
@Override
public void onInput(MaterialDialog dialog, CharSequence input) {
if (input.length() == 0) partPicturesDescription = "No description";
else partPicturesDescription = dialog.getInputEditText().getText().toString();
dialog.dismiss();
Log.d(TAG, "onInput: preExecute");
}
}).show();
PhotoSend ps = new PhotoSend();
ps.execute(partPicturesDescription);
}
final int partscont=imageKeeperList.size（）；
类PhotoSend扩展异步任务{
@凌驾
受保护的void onPreExecute（）{
}
@凌驾
受保护的空位背景（空位…空位）{
最终字符串用户名=”sampleemail@gmail.com";
最终字符串password=“somepassword”；
Properties props=新属性（）；
put（“mail.smtp.host”、“smtp.gmail.com”）；
props.put（“mail.smtp.socketFactory.port”，“465”）；
put（“mail.smtp.socketFactory.class”、“javax.net.ssl.SSLSocketFactory”）；
props.put（“mail.smtp.auth”，“true”）；
props.put（“mail.smtp.port”，“465”）；
Session Session=Session.getDefaultInstance（props，
新的javax.mail.Authenticator（）{
受保护的密码身份验证getPasswordAuthentication（）{
返回新密码身份验证（用户名、密码）；
}
});
试一试{
Message Message=新的mimessage（会话）；
message.setFrom（新的InternetAddress（“sampleemail@gmail.com"));
message.setRecipients（message.RecipientType.TO，InternetAddress.parse（“targetemail@gmail.pl"));
message.setSubject（“电子邮件主题”）；
message.setText（“一些文本”）；
传输。发送（消息）；
Log.d（标签“onInput:background”）；
}捕获（消息异常e）{
抛出新的运行时异常（e）；
}
返回null；
}
@凌驾
受保护的void onPostExecute（void避免）{
Toast.makeText（getContext（），“Sent.”，Toast.LENGTH_SHORT.show（）；
Log.d（标记“onInput:postExecute”）；
}
}
new MaterialDialog.Builder（getContext（））
.内容（“集合描述”）
.inputType（inputType.TYPE\文本\标志\输入\多行）
.input（“简短描述”，“新材料对话框.InputCallback（））{
@凌驾
public void onInput（MaterialDialog对话框，字符序列输入）{
如果（input.length（）==0）partPicturesDescription=“无描述”；
else partPicturesDescription=dialog.GetInputItemText（）.getText（）.toString（）；
dialog.dismise（）；
Log.d（标记“onInput:preExecute”）；
}
}).show（）；
PhotoSend ps=新的PhotoSend（）；
ps.execute（零件图片说明）；
}
我的onPreExecute（）方法中有一个对话框，但它保持不变，首先是doInBackground。让我们看看我是否可以帮助您。因此，首先您对异步任务有一点误用 AsyncTask用于执行一个简短的“后台”操作，将结果返回到UI线程。UI线程是唯一可以接触UI元素而不会发生冲突或崩溃的线程 所以典型的行为是 UI线程->获取用户输入 AsyncTask（后台线程）->发送或处理传入的数据 UI线程->通知用户成功/失败 所以你有两个选择 1） 在启动异步任务之前执行UI对话框
private void getUserInput(){
Session session = Session.getDefaultInstance(props,
new javax.mail.Authenticator() {
protected PasswordAuthentication getPasswordAuthentication() {
doBackgroundProcessing(new PasswordAuthentication(username,password));
}
});
}
private void doBackgroundProcessing(PasswordAuthentication passAuth){
if(passAuth == null || !passAuth.isSuccessful()){ //or whatever success flag they have
Log.e(TAG, "Failed to get credential token");
return;
}
//else we send it to the server it appears based on your code\
showBusyIndicator() //IF you need to block the UI from interacting while you send, NOTE* showBusyIndicator is just a method YOU would create to show one.
new PhotoSend()() {
@Override
public void onPostTask(Boolean wasSuccessful) {
//I recommend actually returning a valid result rather then Void so you know whether or not it succeeded.
if(wasSuccessful){
//close busy indicator, and notify of success
}else{
//close busy indicator, and notify of error
}
}
}
}
protected suspend fun getNameFromDialog(): String? = suspendCancellableCoroutine { c ->
A35Log.v(mClassTag, "getNameFromDialog")
GetTextEntryDialog.newInstance(getParamsForTextDialog(), object : ITextEntryDialogListener {
override fun onTextEntered(text: String) {
if(!c.isCompleted) {
A35Log.v(mClassTag, "User entered name: $text")
c.resume(text)
}
}
override fun onCancel(){
if(!c.isCompleted) {
A35Log.v(mClassTag, "User canceled name entry")
c.resume(null)
}
}
}).show(supportFragmentManager, mClassTag)
}
private fun saveAsDuplicateConfiguration(){
launch(UI){
setIsActionInProgress(true)
val configName = withContext(DefaultDispatcher) { getNameFromDialog() }
if(configName == null){
showFancyToast(getString(R.string.canceled), true, FancyToast.INFO)
}else{
withContext(DefaultDispatcher){
try{
withTimeout(TIMEOUT_FOR_DB_INTERACTION_MS){
A35Log.v(mClassTag, "inserting copy of config with name :$configName")
val configCopy = DeviceAndConfigurationHelper.getCopyOfConfigurationModel(mSelectedConfiguration!!)
configCopy.setConfigName(configName)
configCopy.setDeviceType(FeatureHelper.PRO_DEVICE_KEY) //todo should come from BLE eventually
if(SSDBHelper.insertConfiguration(configCopy) > 0){
showFancyToast(getString(R.string.successfully_saved), true, FancyToast.SUCCESS)
finishCurrentActivity(SSGlobals.TimeOuts.TOAST_DISPLAY_DELAY_CLOSE_MS, true)
}else{
showFancyToast(getString(R.string.error_saving_copy))
}
}
}catch (e: TimeoutCancellationException) {
showFancyToast(getString(R.string.error_timed_out) + ", " + getString(R.string.error_please_try_again_or_press_back), true, FancyToast.ERROR, "TimedOut with error: ${e.message}")
}catch(ex: JobCancellationException){
showFancyToast(getString(R.string.canceled))
}catch(ex: Exception){
showFancyToast(getString(R.string.error_saving_copy) + ", " + getString(R.string.error_please_try_again_or_press_back), true, FancyToast.ERROR, "Error deleting: ${ex.message}")
}finally {
setIsActionInProgress(false)
}
}
}
}
}