Upload Dart Reference Documentation

CkUpload

Current Version: 11.6.1

Chilkat.Upload

Upload files with HTTP POST, form fields, headers, progress tracking, and TLS control.

Chilkat.Upload sends files to a web server using HTTP POST, typically as a multipart/form-data upload. It supports one or more file references, custom form parameters, custom HTTP headers, blocking and asynchronous uploads, progress monitoring, upload throttling, Basic HTTP authentication, proxy settings, HTTPS/TLS configuration, timeout control, and inspection of the HTTP response returned by the server.

File upload requests

Add one or more local file references and send them to a server endpoint using HTTP POST.

Form parameters

Add ordinary form fields alongside file parts when the server expects metadata, tokens, IDs, or other POST parameters.

Custom headers

Include application-specific HTTP headers for authorization schemes, API requirements, content negotiation, or server-side routing.

Blocking or async upload

Use a simple blocking upload, begin an upload in the background, or use async task-based workflows where supported.

Progress and throttling

Monitor bytes sent, percent uploaded, current filename, upload state, and optionally throttle upload bandwidth.

Authentication, proxy, and TLS

Configure Basic authentication, HTTP/SOCKS proxy settings, HTTPS/TLS behavior, cipher restrictions, protocol versions, and certificate pinning.

Common pattern: Set the server Hostname, Port, Ssl, and upload Path, add file references with AddFileReference, add any form parameters or headers, then call BlockingUpload or start an asynchronous upload. After completion, inspect ResponseStatus, ResponseHeader, ResponseBody, and LastErrorText to determine what the server returned.

Object Creation

// pubspec.yaml:
//     dependencies:
//       chilkat: ^11.6.1

import 'package:chilkat/chilkat.dart';

// Once per process, before any other Chilkat call:
Chilkat.unlockBundle('Anything for 30-day trial');   // shorthand for CkGlobal().unlockBundle(..)

final upload = CkUpload();
// ... the native object is released when `upload` is garbage collected, or now with upload.dispose().
CkUpload CkUpload()

Creates the underlying native Chilkat object. Use a CkUpload only from the isolate that created it: Chilkat objects cannot be sent between isolates. Every call is synchronous; in a Flutter app, run long operations (network, large files) inside Isolate.run, creating the Chilkat objects inside the isolate.

void dispose()

Releases the native object immediately instead of waiting for garbage collection (useful for a large CkBinData or an open socket). Calling it more than once is harmless; any other use of the object afterwards throws a StateError. isDisposed tells whether it has been called.

Errors

A method that can fail throws a ChilkatException: a method whose only outcome is success or failure returns void and throws on failure; a method producing a String or an object returns it and throws where Chilkat would have returned null. The exception carries the object's LastErrorText at the time of the failure (lastErrorText), the class and method names (className, methodName) and a one-line message. Properties never throw, and methods that answer a question (has..., is..., ...) return a plain bool.

try {
  upload.someMethod(...);
} on ChilkatException catch (e) {
  print(e);                // CkUpload.someMethod failed: <reason>
  print(e.lastErrorText);  // the full Chilkat log of the failed call
}

Properties

AbortCurrent
// read/write
bool get abortCurrent
set abortCurrent(bool value)
Introduced in version 9.5.0.58

When set to true, causes the currently running method to abort. Methods that always finish quickly (i.e.have no length file operations or network communications) are not affected. If no method is running, then this property is automatically reset to false when the next method is called. When the abort occurs, this property is reset to false. Both synchronous and asynchronous method calls can be aborted. (A synchronous method call could be aborted by setting this property from a separate thread.)

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BandwidthThrottleUp
// read/write
int get bandwidthThrottleUp
set bandwidthThrottleUp(int value)
Introduced in version 9.5.0.49

If non-zero, limits (throttles) the upload bandwidth to approximately this maximum number of bytes per second. The default value of this property is 0.

More Information and Examples
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ChunkSize
// read/write
int get chunkSize
set chunkSize(int value)

The chunk size (in bytes) used by the underlying TCP/IP sockets for uploading files. The default value is 65535.

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ClientIpAddress
// read/write
String get clientIpAddress
set clientIpAddress(String value)
Introduced in version 9.5.0.49

The IP address to use for computers with multiple network interfaces or IP addresses. For computers with a single network interface (i.e. most computers), this property should not be set. For multihoming computers, the default IP address is automatically used if this property is not set.

The IP address is a string such as in dotted notation using numbers, not domain names, such as 165.164.55.124.

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CurrentFilename
// read-only
String get currentFilename
Introduced in version 9.5.0.90

The current filename being uploaded while an asynchronous upload is in progress.

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DebugLogFilePath
// read/write
String get debugLogFilePath
set debugLogFilePath(String value)

If set to a file path, this property logs the LastErrorText of each Chilkat method or property call to the specified file. This logging helps identify the context and history of Chilkat calls leading up to any crash or hang, aiding in debugging.

Enabling the VerboseLogging property provides more detailed information. This property is mainly used for debugging rare instances where a Chilkat method call causes a hang or crash, which should generally not happen.

Possible causes of hangs include:

  • A timeout property set to 0, indicating an infinite timeout.
  • A hang occurring within an event callback in the application code.
  • An internal bug in the Chilkat code causing the hang.

More Information and Examples
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Expect100Continue
// read/write
bool get expect100Continue
set expect100Continue(bool value)

When true, the request header will included an Expect: 100-continue header field. This indicates that the server should respond with an intermediate response of 100 Continue or 417 Expectation Failed response based on the information available in the request header. This helps avoid situations such as limits on upload sizes. It allows the server to reject the upload, and then the client can abort prior to uploading the data.

The default value of this property is true.

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HeartbeatMs
// read/write
int get heartbeatMs
set heartbeatMs(int value)

The interval in milliseconds between each AbortCheck event callback, which enables an application to abort certain method calls before they complete. By default, HeartbeatMs is set to 0, meaning no AbortCheck event callbacks will trigger.

More Information and Examples
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Hostname
// read/write
String get hostname
set hostname(String value)

The hostname of the HTTP server that is the target of the upload. Do not include http:// in the hostname. It can be a hostname, such as www.chilkatsoft.com, or an IP address, such as 168.144.70.227.

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IdleTimeoutMs
// read/write
int get idleTimeoutMs
set idleTimeoutMs(int value)

A timeout in milliseconds. The default value is 30000. If the upload hangs (i.e. progress halts) for more than this time, the component will abort the upload. (It will timeout.)

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LastErrorHtml
// read-only
String get lastErrorHtml

Provides HTML-formatted information about the last called method or property. If a method call fails or behaves unexpectedly, check this property for details. Note that information is available regardless of the method call's success.

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LastErrorText
// read-only
String get lastErrorText

Provides plain text information about the last called method or property. If a method call fails or behaves unexpectedly, check this property for details. Note that information is available regardless of the method call's success.

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LastErrorXml
// read-only
String get lastErrorXml

Provides XML-formatted information about the last called method or property. If a method call fails or behaves unexpectedly, check this property for details. Note that information is available regardless of the method call's success.

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LastMethodSuccess
// read/write
bool get lastMethodSuccess
set lastMethodSuccess(bool value)

Indicates the success or failure of the most recent method call: true means success, false means failure. This property remains unchanged by property setters or getters. This method is present to address challenges in checking for null or Nothing returns in certain programming languages. Note: This property does not apply to methods that return integer values or to boolean-returning methods where the boolean does not indicate success or failure.

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Login
// read/write
String get login
set login(String value)

The HTTP login for sites requiring authentication. Chilkat Upload supports Basic HTTP authentication.

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NumBytesSent
// read-only
int get numBytesSent

After an upload has completed, this property contains the number of bytes sent. During asynchronous uploads, this property contains the current number of bytes sent while the upload is in progress.

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Password
// read/write
String get password
set password(String value)

The HTTP password for sites requiring authentication. Chilkat Upload supports Basic HTTP authentication.

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Path
// read/write
String get path
set path(String value)

The path part of the upload URL. Some examples:

desc> If the upload target (i.e. consumer) URL is: http://www.freeaspupload.net/freeaspupload/testUpload.asp, then

Hostname = www.freeaspupload.net Path = /freeaspupload/testUpload.asp
If the upload target URL is https://www.chilkatsoft.com/cgi-bin/ConsumeUpload.exe, then
Hostname = www.chilkatsoft.com Path = /cgi-bin/ConsumeUpload.exe

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PercentDoneScale
// read/write
int get percentDoneScale
set percentDoneScale(int value)
Introduced in version 9.5.0.49

This property is only valid in programming environment and languages that allow for event callbacks.

Sets the value to be defined as 100% complete for the purpose of PercentDone event callbacks. The defaut value of 100 means that at most 100 event PercentDone callbacks will occur in a method that (1) is event enabled and (2) is such that it is possible to measure progress as a percentage completed. This property may be set to larger numbers to get more fine-grained PercentDone callbacks. For example, setting this property equal to 1000 will provide callbacks with .1 percent granularity. For example, a value of 453 would indicate 45.3% competed. This property is clamped to a minimum value of 10, and a maximum value of 100000.

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PercentUploaded
// read-only
int get percentUploaded

Contains the current percentage completion (0 to 100) while an asynchronous upload is in progress.

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Port
// read/write
int get port
set port(int value)

The port number of the upload target (i.e. consumer) URL. The default value is 80. If SSL is used, this should be set to 443 (typically).

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PreferIpv6
// read/write
bool get preferIpv6
set preferIpv6(bool value)

If true, then use IPv6 over IPv4 when both are supported for a particular domain. The default value of this property is false, which will choose IPv4 over IPv6.

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ProxyDomain
// read/write
String get proxyDomain
set proxyDomain(String value)

The domain name of a proxy host if an HTTP proxy is used. Do not include the http://. The domain name may be a hostname, such as www.chilkatsoft.com, or an IP address, such as 168.144.70.227.

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ProxyLogin
// read/write
String get proxyLogin
set proxyLogin(String value)

If an HTTP proxy is used and it requires authentication, this property specifies the HTTP proxy login.

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ProxyPassword
// read/write
String get proxyPassword
set proxyPassword(String value)

If an HTTP proxy is used and it requires authentication, this property specifies the HTTP proxy password.

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ProxyPort
// read/write
int get proxyPort
set proxyPort(int value)

The port number of a proxy server if an HTTP proxy is used.

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ResponseBodyStr
// read-only
String get responseBodyStr
Introduced in version 9.5.0.83

Returns the response body as a string.

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ResponseHeader
// read-only
String get responseHeader

An HTTP upload is nothing more than an HTTP POST that contains the content of the files being uploaded. Just as with any HTTP POST or GET, the server should send an HTTP response that consists of header and body.

desc>This property contains the header part of the HTTP response.

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ResponseStatus
// read-only
int get responseStatus

The HTTP response status code of the HTTP response. A list of HTTP status codes can be found here: HTTP Response Status Codes.

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Ssl
// read/write
bool get ssl
set ssl(bool value)

Set this to true if the upload is to HTTPS. For example, if the target of the upload is:

https://www.myuploadtarget.com/consumeUpload.asp

desc>then set:

Ssl = true
Hostname = www.myuploadtarget.com
Path = /consumeupload.asp
Port = 443

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SslAllowedCiphers
// read/write
String get sslAllowedCiphers
set sslAllowedCiphers(String value)
Introduced in version 9.5.0.55

Provides a means for setting a list of ciphers that are allowed for SSL/TLS connections. The default (empty string) indicates that all implemented ciphers are possible. The TLS ciphers supported in Chilkat v9.5.0.55 and later are:

TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305_SHA256
TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305_SHA256
TLS_DHE_RSA_WITH_CHACHA20_POLY1305_SHA256
TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA
TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256
TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA
TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA384
TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384
TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384
TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA
TLS_DHE_RSA_WITH_AES_256_CBC_SHA256
TLS_DHE_RSA_WITH_AES_256_GCM_SHA384
TLS_DHE_RSA_WITH_AES_256_CBC_SHA
TLS_RSA_WITH_AES_256_CBC_SHA256
TLS_RSA_WITH_AES_256_GCM_SHA384
TLS_RSA_WITH_AES_256_CBC_SHA
TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256
TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256
TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA
TLS_DHE_RSA_WITH_AES_128_CBC_SHA256
TLS_DHE_RSA_WITH_AES_128_GCM_SHA256
TLS_DHE_RSA_WITH_AES_128_CBC_SHA
TLS_RSA_WITH_AES_128_CBC_SHA256
TLS_RSA_WITH_AES_128_GCM_SHA256
TLS_RSA_WITH_AES_128_CBC_SHA
TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA
TLS_DHE_RSA_WITH_3DES_EDE_CBC_SHA
TLS_RSA_WITH_3DES_EDE_CBC_SHA
TLS_ECDHE_RSA_WITH_RC4_128_SHA
TLS_RSA_WITH_RC4_128_SHA
TLS_RSA_WITH_RC4_128_MD5
TLS_DHE_RSA_WITH_DES_CBC_SHA
TLS_RSA_WITH_DES_CBC_SHA
To restrict SSL/TLS connections to one or more specific ciphers, set this property to a comma-separated list of ciphers such as TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384, TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384. The order should be in terms of preference, with the preferred algorithms listed first. (Note that the client cannot specifically choose the algorithm is picked because it is the server that chooses. The client simply provides the server with a list from which to choose.)

The property can also disallow connections with servers having certificates with RSA keys less than a certain size. By default, server certificates having RSA keys of 512 bits or greater are allowed. Add the keyword rsa1024 to disallow connections with servers having keys smaller than 1024 bits. Add the keyword rsa2048 to disallow connections with servers having keys smaller than 2048 bits.

Note: Prior to Chilkat v9.5.0.55, it was not possible to explicitly list allowed cipher suites. The deprecated means for indicating allowed ciphers was both incomplete and unprecise. For example, the following keywords could be listed to allow matching ciphers: aes256-cbc, aes128-cbc, 3des-cbc, and rc4. These keywords will still be recognized, but programs should be updated to explicitly list the allowed ciphers.

secure-renegotiation: Starting in Chilkat v9.5.0.55, the keyword secure-renegotiation may be added to require that all renegotions be done securely (as per RFC 5746).

best-practices: Starting in Chilkat v9.5.0.55, this property may be set to the single keyword best-practices. This will allow ciphers based on the current best practices. As new versions of Chilkat are released, the best practices may change. Changes will be noted here. The current best practices are:

  • If the server uses an RSA key, it must be 1024 bits or greater.
  • All renegotations must be secure renegotiations.
  • All ciphers using RC4, DES, or 3DES are disallowed.

Example: The following string would restrict to 2 specific cipher suites, require RSA keys to be 1024 bits or greater, and require secure renegotiations: TLS_DHE_RSA_WITH_AES_256_CBC_SHA256, TLS_RSA_WITH_AES_256_CBC_SHA, rsa1024, secure-renegotiation

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SslProtocol
// read/write
String get sslProtocol
set sslProtocol(String value)
Introduced in version 9.5.0.55

Selects the secure protocol to be used for secure (SSL/TLS) connections. Possible values are:

default
TLS 1.3
TLS 1.2
TLS 1.1
TLS 1.0
SSL 3.0
TLS 1.3 or higher
TLS 1.2 or higher
TLS 1.1 or higher
TLS 1.0 or higher
The default value is default which will choose the, which allows for the protocol to be selected dynamically at runtime based on the requirements of the server. Choosing an exact protocol will cause the connection to fail unless that exact protocol is negotiated. It is better to choose X or higher than an exact protocol. The default is effectively SSL 3.0 or higher.

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TlsPinSet
// read/write
String get tlsPinSet
set tlsPinSet(String value)
Introduced in version 9.5.0.55

Specifies a set of pins for Public Key Pinning for TLS connections. This property lists the expected SPKI fingerprints for the server certificates. If the server's certificate (sent during the TLS handshake) does not match any of the SPKI fingerprints, then the TLS handshake is aborted and the connection fails. The format of this string property is as follows:

hash_algorithm, encoding, SPKI_fingerprint_1, SPKI_fingerprint_2, ...
For example, the following string specifies a single sha256 base64-encoded SPKI fingerprint:
"sha256, base64, lKg1SIqyhPSK19tlPbjl8s02yChsVTDklQpkMCHvsTE="
This example specifies two SPKI fingerprints:
"sha256, base64, 4t37LpnGmrMEAG8HEz9yIrnvJV2euVRwCLb9EH5WZyI=, 68b0G5iqMvWVWvUCjMuhLEyekM5729PadtnU5tdXZKs="
Any of the following hash algorithms are allowed:.sha1, sha256, sha384, sha512, md2, md5, haval, ripemd128, ripemd160,ripemd256, or ripemd320.

The following encodings are allowed: base64, hex, and any of the encodings indicated in the link below.

More Information and Examples
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TotalUploadSize
// read-only
int get totalUploadSize

The total size of the upload (in bytes). This property will become set at the beginning of an asynchronous upload. A program may monitor asynchronous uploads by tracking both NumBytesSent and PercentUploaded.

desc> This property is also set during synchronous uploads.

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UploadInProgress
// read-only
bool get uploadInProgress

Set to true when an asynchronous upload is started. When the asynchronous upload is complete, this property becomes equal to false. A program will typically begin an asynchronous upload by calling BeginUpload, and then periodically checking the value of this property to determine when the upload is complete.

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UploadSuccess
// read-only
bool get uploadSuccess

Set to true (success) or false (failed) after an asynchronous upload completes or aborts due to failure. When a program does an asynchronous upload, it will wait until UploadInProgress becomes false. It will then check the value of this property to determine if the upload was successful or not.

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VerboseLogging
// read/write
bool get verboseLogging
set verboseLogging(bool value)

If set to true, then the contents of LastErrorText (or LastErrorXml, or LastErrorHtml) may contain more verbose information. The default value is false. Verbose logging should only be used for debugging. The potentially large quantity of logged information may adversely affect peformance.

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Version
// read-only
String get version

Version of the component/library, such as "10.1.0"

More Information and Examples
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Methods

AbortUpload
void abortUpload()

May be called during an asynchronous upload to abort.

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AddCustomHeader
void addCustomHeader(String name, String value)

Adds a custom HTTP header to the HTTP upload.

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AddFileReference
void addFileReference(String name, String filename)

Adds a file to the list of files to be uploaded in the next call to BlockingUpload, BeginUpload, or UploadToMemory. To upload more than one file, call this method once for each file to be uploaded.

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AddParam
void addParam(String name, String value)

Adds a custom HTTP request parameter to the upload.

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BeginUpload
void beginUpload()

Starts an asynchronous upload. Only one asynchronous upload may be in progress at a time. To achieve multiple asynchronous uploads, use multiple instances of the Chilkat Upload object. Each object instance is capable of managing a single asynchronous upload.

desc> When this method is called, a background thread is started and the asynchronous upload runs in the background. The upload may be aborted at any time by calling AbortUpload. The upload is completed (or failed) when UploadInProgress becomes false. At that point, the UploadSuccess property may be checked to determine success (true) or failure (false).

Returns normally on success; throws a ChilkatException on failure.

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BlockingUpload
void blockingUpload()

Uploads files to a web server using HTTP. The files to be uploaded are indicated by calling AddFileReference once for each file (prior to calling this method).

Returns normally on success; throws a ChilkatException on failure.

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ClearFileReferences
void clearFileReferences()

Clears the internal list of files created by calls to AddFileReference.

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ClearParams
void clearParams()

Clears the internal list of params created by calls to AddParam.

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SleepMs
void sleepMs(int millisec)

A convenience method for putting the calling process to sleep for N milliseconds. It is provided here because some programming languages do not provide this capability, and sleeping for short increments of time is helpful when doing asynchronous uploads.

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Events

All Chilkat methods are synchronous: the call returns when the work is done. During a call, CkUpload raises three events so your application can show progress and offer a way out. Each event is a nullable callback property on the object; assign a function to receive it, or null to stop receiving it:

final upload = CkUpload();
upload.onPercentDone = (pct) {
  print('$pct%');
  return false;   // return true to abort the method in progress
};
upload.onProgressInfo = (name, value) => print('$name: $value');
upload.heartbeatMs = 250;   // raise onAbortCheck 4 times per second during Chilkat calls
upload.onAbortCheck = () => _userPressedCancel;

AbortCheck fires at regular intervals controlled by the HeartbeatMs property (0, the default, disables it); PercentDone fires when an operation's completion percentage is known; ProgressInfo delivers named progress values. Returning true from onAbortCheck or onPercentDone aborts the running method, which then throws a ChilkatException.

Events fire on the thread that called the method, before that method returns. An exception thrown inside a callback aborts the running method and is rethrown from it once the native library has returned. In a Flutter app the callbacks run inside the worker isolate that owns the object; forward progress to the UI through a SendPort, and let onAbortCheck read a flag the UI sets the same way.

AbortCheck
// callback property; return true to abort the method in progress
bool Function()? onAbortCheck

Enables a method call to be aborted by triggering the AbortCheck event at intervals defined by the HeartbeatMs property. If HeartbeatMs is set to its default value of 0, no events will occur. For instance, set HeartbeatMs to 200 to trigger 5 AbortCheck events per second.

More Information and Examples

Example:

upload.heartbeatMs = 250;   // call onAbortCheck 4 times per second

var cancelRequested = false;
upload.onAbortCheck = () => cancelRequested;
// ... set cancelRequested = true (e.g. from a message received on a ReceivePort) to abort the method in progress
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PercentDone
// callback property; return true to abort the method in progress
bool Function(int pctDone)? onPercentDone

This provides the percentage completion for any method involving network communications or time-consuming processing, assuming the progress can be measured as a percentage. This event is triggered only when it's possible and logical to express the operation's progress as a percentage. The pctDone argument will range from 1 to 100. For methods that finish quickly, the number of PercentDone callbacks may vary, but the final callback will have pctDone equal to 100. For longer operations, callbacks will not exceed one per percentage point (e.g., 1, 2, 3, ..., 98, 99, 100).

The PercentDone callback also acts as an AbortCheck event. For fast methods where PercentDone fires, an AbortCheck event may not trigger since the PercentDone callback already provides an opportunity to abort. For longer operations, where time between PercentDone callbacks is extended, AbortCheck callbacks enable more responsive operation termination.

To abort the operation, set the abort output argument to true. This will cause the method to terminate and return a failure status or corresponding failure value.

More Information and Examples

Example:

upload.onPercentDone = (pct) {
  // pct ranges from 1 to 100.
  print('Percent done: $pct');
  return false;   // return true to abort the method in progress
};
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ProgressInfo
// callback property
void Function(String name, String value)? onProgressInfo

This event callback provides tag name/value pairs that detail what occurs during a method call. To discover existing tag names, create code to handle the event, emit the pairs, and review them. Most tag names are self-explanatory.

Note: Some Chilkat methods don't fire any ProgressInfo events.

More Information and Examples

Example:

upload.onProgressInfo = (name, value) => print('$name: $value');
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