# Print output for @column tags ?>
public
class
WebViewClient
extends Object
java.lang.Object | |
↳ | android.webkit.WebViewClient |
Constants | |
---|---|
int |
ERROR_AUTHENTICATION
User authentication failed on server |
int |
ERROR_BAD_URL
Malformed URL |
int |
ERROR_CONNECT
Failed to connect to the server |
int |
ERROR_FAILED_SSL_HANDSHAKE
Failed to perform SSL handshake |
int |
ERROR_FILE
Generic file error |
int |
ERROR_FILE_NOT_FOUND
File not found |
int |
ERROR_HOST_LOOKUP
Server or proxy hostname lookup failed |
int |
ERROR_IO
Failed to read or write to the server |
int |
ERROR_PROXY_AUTHENTICATION
User authentication failed on proxy |
int |
ERROR_REDIRECT_LOOP
Too many redirects |
int |
ERROR_TIMEOUT
Connection timed out |
int |
ERROR_TOO_MANY_REQUESTS
Too many requests during this load |
int |
ERROR_UNKNOWN
Generic error |
int |
ERROR_UNSAFE_RESOURCE
Resource load was canceled by Safe Browsing |
int |
ERROR_UNSUPPORTED_AUTH_SCHEME
Unsupported authentication scheme (not basic or digest) |
int |
ERROR_UNSUPPORTED_SCHEME
Unsupported URI scheme |
int |
SAFE_BROWSING_THREAT_BILLING
The resource was blocked because it may trick the user into a billing agreement. |
int |
SAFE_BROWSING_THREAT_MALWARE
The resource was blocked because it contains malware. |
int |
SAFE_BROWSING_THREAT_PHISHING
The resource was blocked because it contains deceptive content. |
int |
SAFE_BROWSING_THREAT_UNKNOWN
The resource was blocked for an unknown reason. |
int |
SAFE_BROWSING_THREAT_UNWANTED_SOFTWARE
The resource was blocked because it contains unwanted software. |
Public constructors | |
---|---|
WebViewClient()
|
Public methods | |
---|---|
void
|
doUpdateVisitedHistory(WebView view, String url, boolean isReload)
Notify the host application to update its visited links database. |
void
|
onFormResubmission(WebView view, Message dontResend, Message resend)
As the host application if the browser should resend data as the requested page was a result of a POST. |
void
|
onLoadResource(WebView view, String url)
Notify the host application that the WebView will load the resource specified by the given url. |
void
|
onPageCommitVisible(WebView view, String url)
Notify the host application that |
void
|
onPageFinished(WebView view, String url)
Notify the host application that a page has finished loading. |
void
|
onPageStarted(WebView view, String url, Bitmap favicon)
Notify the host application that a page has started loading. |
void
|
onReceivedClientCertRequest(WebView view, ClientCertRequest request)
Notify the host application to handle a SSL client certificate request. |
void
|
onReceivedError(WebView view, int errorCode, String description, String failingUrl)
This method is deprecated.
Use |
void
|
onReceivedError(WebView view, WebResourceRequest request, WebResourceError error)
Report web resource loading error to the host application. |
void
|
onReceivedHttpAuthRequest(WebView view, HttpAuthHandler handler, String host, String realm)
Notifies the host application that the WebView received an HTTP authentication request. |
void
|
onReceivedHttpError(WebView view, WebResourceRequest request, WebResourceResponse errorResponse)
Notify the host application that an HTTP error has been received from the server while loading a resource. |
void
|
onReceivedLoginRequest(WebView view, String realm, String account, String args)
Notify the host application that a request to automatically log in the user has been processed. |
void
|
onReceivedSslError(WebView view, SslErrorHandler handler, SslError error)
Notify the host application that an SSL error occurred while loading a resource. |
boolean
|
onRenderProcessGone(WebView view, RenderProcessGoneDetail detail)
Notify host application that the given WebView's render process has exited. |
void
|
onSafeBrowsingHit(WebView view, WebResourceRequest request, int threatType, SafeBrowsingResponse callback)
Notify the host application that a loading URL has been flagged by Safe Browsing. |
void
|
onScaleChanged(WebView view, float oldScale, float newScale)
Notify the host application that the scale applied to the WebView has changed. |
void
|
onTooManyRedirects(WebView view, Message cancelMsg, Message continueMsg)
This method is deprecated. This method is no longer called. When the WebView encounters a redirect loop, it will cancel the load. |
void
|
onUnhandledKeyEvent(WebView view, KeyEvent event)
Notify the host application that a key was not handled by the WebView. |
WebResourceResponse
|
shouldInterceptRequest(WebView view, WebResourceRequest request)
Notify the host application of a resource request and allow the application to return the data. |
WebResourceResponse
|
shouldInterceptRequest(WebView view, String url)
This method is deprecated.
Use |
boolean
|
shouldOverrideKeyEvent(WebView view, KeyEvent event)
Give the host application a chance to handle the key event synchronously. |
boolean
|
shouldOverrideUrlLoading(WebView view, WebResourceRequest request)
Give the host application a chance to take control when a URL is about to be loaded in the current WebView. |
boolean
|
shouldOverrideUrlLoading(WebView view, String url)
This method is deprecated.
Use |
Inherited methods | |
---|---|
public static final int ERROR_AUTHENTICATION
User authentication failed on server
Constant Value: -4 (0xfffffffc)
public static final int ERROR_BAD_URL
Malformed URL
Constant Value: -12 (0xfffffff4)
public static final int ERROR_CONNECT
Failed to connect to the server
Constant Value: -6 (0xfffffffa)
public static final int ERROR_FAILED_SSL_HANDSHAKE
Failed to perform SSL handshake
Constant Value: -11 (0xfffffff5)
public static final int ERROR_FILE
Generic file error
Constant Value: -13 (0xfffffff3)
public static final int ERROR_FILE_NOT_FOUND
File not found
Constant Value: -14 (0xfffffff2)
public static final int ERROR_HOST_LOOKUP
Server or proxy hostname lookup failed
Constant Value: -2 (0xfffffffe)
public static final int ERROR_IO
Failed to read or write to the server
Constant Value: -7 (0xfffffff9)
public static final int ERROR_PROXY_AUTHENTICATION
User authentication failed on proxy
Constant Value: -5 (0xfffffffb)
public static final int ERROR_REDIRECT_LOOP
Too many redirects
Constant Value: -9 (0xfffffff7)
public static final int ERROR_TIMEOUT
Connection timed out
Constant Value: -8 (0xfffffff8)
public static final int ERROR_TOO_MANY_REQUESTS
Too many requests during this load
Constant Value: -15 (0xfffffff1)
public static final int ERROR_UNKNOWN
Generic error
Constant Value: -1 (0xffffffff)
public static final int ERROR_UNSAFE_RESOURCE
Resource load was canceled by Safe Browsing
Constant Value: -16 (0xfffffff0)
public static final int ERROR_UNSUPPORTED_AUTH_SCHEME
Unsupported authentication scheme (not basic or digest)
Constant Value: -3 (0xfffffffd)
public static final int ERROR_UNSUPPORTED_SCHEME
Unsupported URI scheme
Constant Value: -10 (0xfffffff6)
public static final int SAFE_BROWSING_THREAT_BILLING
The resource was blocked because it may trick the user into a billing agreement.
This constant is only used when targetSdkVersion is at least Build.VERSION_CODES.Q
. Otherwise, SAFE_BROWSING_THREAT_UNKNOWN
is used
instead.
Constant Value: 4 (0x00000004)
public static final int SAFE_BROWSING_THREAT_MALWARE
The resource was blocked because it contains malware.
Constant Value: 1 (0x00000001)
public static final int SAFE_BROWSING_THREAT_PHISHING
The resource was blocked because it contains deceptive content.
Constant Value: 2 (0x00000002)
public static final int SAFE_BROWSING_THREAT_UNKNOWN
The resource was blocked for an unknown reason.
Constant Value: 0 (0x00000000)
public static final int SAFE_BROWSING_THREAT_UNWANTED_SOFTWARE
The resource was blocked because it contains unwanted software.
Constant Value: 3 (0x00000003)
public WebViewClient ()
public void doUpdateVisitedHistory (WebView view, String url, boolean isReload)
Notify the host application to update its visited links database.
Parameters | |
---|---|
view |
WebView : The WebView that is initiating the callback. |
url |
String : The url being visited. |
isReload |
boolean : true if this url is being reloaded. |
public void onFormResubmission (WebView view, Message dontResend, Message resend)
As the host application if the browser should resend data as the requested page was a result of a POST. The default is to not resend the data.
Parameters | |
---|---|
view |
WebView : The WebView that is initiating the callback. |
dontResend |
Message : The message to send if the browser should not resend |
resend |
Message : The message to send if the browser should resend data |
public void onLoadResource (WebView view, String url)
Notify the host application that the WebView will load the resource specified by the given url.
Parameters | |
---|---|
view |
WebView : The WebView that is initiating the callback. |
url |
String : The url of the resource the WebView will load. |
public void onPageCommitVisible (WebView view, String url)
Notify the host application that WebView
content left over from
previous page navigations will no longer be drawn.
This callback can be used to determine the point at which it is safe to make a recycled
WebView
visible, ensuring that no stale content is shown. It is called
at the earliest point at which it can be guaranteed that WebView#onDraw
will no
longer draw any content from previous navigations. The next draw will display either the
background color
of the WebView
, or some of the
contents of the newly loaded page.
This method is called when the body of the HTTP response has started loading, is reflected in the DOM, and will be visible in subsequent draws. This callback occurs early in the document loading process, and as such you should expect that linked resources (for example, CSS and images) may not be available.
For more fine-grained notification of visual state updates, see WebView.postVisualStateCallback(long, WebView.VisualStateCallback)
.
Please note that all the conditions and recommendations applicable to
WebView#postVisualStateCallback
also apply to this API.
This callback is only called for main frame navigations.
Parameters | |
---|---|
view |
WebView : The WebView for which the navigation occurred. |
url |
String : The URL corresponding to the page navigation that triggered this callback. |
public void onPageFinished (WebView view, String url)
Notify the host application that a page has finished loading. This method
is called only for main frame. Receiving an onPageFinished()
callback does not
guarantee that the next frame drawn by WebView will reflect the state of the DOM at this
point. In order to be notified that the current DOM state is ready to be rendered, request a
visual state callback with WebView#postVisualStateCallback
and wait for the supplied
callback to be triggered.
Parameters | |
---|---|
view |
WebView : The WebView that is initiating the callback. |
url |
String : The url of the page. |
public void onPageStarted (WebView view, String url, Bitmap favicon)
Notify the host application that a page has started loading. This method is called once for each main frame load so a page with iframes or framesets will call onPageStarted one time for the main frame. This also means that onPageStarted will not be called when the contents of an embedded frame changes, i.e. clicking a link whose target is an iframe, it will also not be called for fragment navigations (navigations to #fragment_id).
Parameters | |
---|---|
view |
WebView : The WebView that is initiating the callback. |
url |
String : The url to be loaded. |
favicon |
Bitmap : The favicon for this page if it already exists in the
database. |
public void onReceivedClientCertRequest (WebView view, ClientCertRequest request)
Notify the host application to handle a SSL client certificate request. The host application
is responsible for showing the UI if desired and providing the keys. There are three ways to
respond: ClientCertRequest#proceed
, ClientCertRequest#cancel
, or ClientCertRequest.ignore()
. Webview stores the response in memory (for the life of the
application) if ClientCertRequest#proceed
or ClientCertRequest#cancel
is
called and does not call onReceivedClientCertRequest()
again for the same host and
port pair. Webview does not store the response if ClientCertRequest#ignore
is called. Note that, multiple layers in chromium network stack might be
caching the responses, so the behavior for ignore is only a best case
effort.
This method is called on the UI thread. During the callback, the
connection is suspended.
For most use cases, the application program should implement the
KeyChainAliasCallback
interface and pass it to
KeyChain.choosePrivateKeyAlias(Activity, KeyChainAliasCallback, String[], Principal[], Uri, String)
to start an
activity for the user to choose the proper alias. The keychain activity will
provide the alias through the callback method in the implemented interface. Next
the application should create an async task to call
KeyChain.getPrivateKey(Context, String)
to receive the key.
An example implementation of client certificates can be seen at
AOSP Browser
The default behavior is to cancel, returning no client certificate.
Parameters | |
---|---|
view |
WebView : The WebView that is initiating the callback |
request |
ClientCertRequest : An instance of a ClientCertRequest |
public void onReceivedError (WebView view, int errorCode, String description, String failingUrl)
This method is deprecated.
Use onReceivedError(WebView, WebResourceRequest, WebResourceError)
instead.
Report an error to the host application. These errors are unrecoverable
(i.e. the main resource is unavailable). The errorCode
parameter
corresponds to one of the ERROR_*
constants.
Parameters | |
---|---|
view |
WebView : The WebView that is initiating the callback. |
errorCode |
int : The error code corresponding to an ERROR_* value. |
description |
String : A String describing the error. |
failingUrl |
String : The url that failed to load. |
public void onReceivedError (WebView view, WebResourceRequest request, WebResourceError error)
Report web resource loading error to the host application. These errors usually indicate inability to connect to the server. Note that unlike the deprecated version of the callback, the new version will be called for any resource (iframe, image, etc.), not just for the main page. Thus, it is recommended to perform minimum required work in this callback.
Parameters | |
---|---|
view |
WebView : The WebView that is initiating the callback. |
request |
WebResourceRequest : The originating request. |
error |
WebResourceError : Information about the error occurred. |
public void onReceivedHttpAuthRequest (WebView view, HttpAuthHandler handler, String host, String realm)
Notifies the host application that the WebView received an HTTP
authentication request. The host application can use the supplied
HttpAuthHandler
to set the WebView's response to the request.
The default behavior is to cancel the request.
Parameters | |
---|---|
view |
WebView : the WebView that is initiating the callback |
handler |
HttpAuthHandler : the HttpAuthHandler used to set the WebView's response |
host |
String : the host requiring authentication |
realm |
String : the realm for which authentication is required |
public void onReceivedHttpError (WebView view, WebResourceRequest request, WebResourceResponse errorResponse)
Notify the host application that an HTTP error has been received from the server while
loading a resource. HTTP errors have status codes >= 400. This callback will be called
for any resource (iframe, image, etc.), not just for the main page. Thus, it is recommended
to perform minimum required work in this callback. Note that the content of the server
response may not be provided within the errorResponse
parameter.
Parameters | |
---|---|
view |
WebView : The WebView that is initiating the callback. |
request |
WebResourceRequest : The originating request. |
errorResponse |
WebResourceResponse : Information about the error occurred. |
public void onReceivedLoginRequest (WebView view, String realm, String account, String args)
Notify the host application that a request to automatically log in the user has been processed.
Parameters | |
---|---|
view |
WebView : The WebView requesting the login. |
realm |
String : The account realm used to look up accounts. |
account |
String : An optional account. If not null , the account should be
checked against accounts on the device. If it is a valid
account, it should be used to log in the user.
This value may be null . |
args |
String : Authenticator specific arguments used to log in the user. |
public void onReceivedSslError (WebView view, SslErrorHandler handler, SslError error)
Notify the host application that an SSL error occurred while loading a
resource. The host application must call either SslErrorHandler#cancel
or
SslErrorHandler#proceed
. Note that the decision may be retained for use in
response to future SSL errors. The default behavior is to cancel the
load.
This API is only called for recoverable SSL certificate errors. In the case of
non-recoverable errors (such as when the server fails the client), WebView will call onReceivedError(android.webkit.WebView, android.webkit.WebResourceRequest, android.webkit.WebResourceError)
with ERROR_FAILED_SSL_HANDSHAKE
.
Applications are advised not to prompt the user about SSL errors, as the user is unlikely to be able to make an informed security decision and WebView does not provide any UI for showing the details of the error in a meaningful way.
Application overrides of this method may display custom error pages or
silently log issues, but it is strongly recommended to always call
SslErrorHandler#cancel
and never allow proceeding past errors.
Parameters | |
---|---|
view |
WebView : The WebView that is initiating the callback. |
handler |
SslErrorHandler : An SslErrorHandler that will handle the user's
response. |
error |
SslError : The SSL error object. |
public boolean onRenderProcessGone (WebView view, RenderProcessGoneDetail detail)
Notify host application that the given WebView's render process has exited.
Multiple WebView instances may be associated with a single render process;
onRenderProcessGone will be called for each WebView that was affected.
The application's implementation of this callback should only attempt to
clean up the specific WebView given as a parameter, and should not assume
that other WebView instances are affected.
The given WebView can't be used, and should be removed from the view hierarchy,
all references to it should be cleaned up, e.g any references in the Activity
or other classes saved using View.findViewById(int)
and similar calls, etc.
To cause an render process crash for test purpose, the application can
call loadUrl("chrome://crash")
on the WebView. Note that multiple WebView
instances may be affected if they share a render process, not just the
specific WebView which loaded chrome://crash.
Parameters | |
---|---|
view |
WebView : The WebView which needs to be cleaned up. |
detail |
RenderProcessGoneDetail : the reason why it exited. |
Returns | |
---|---|
boolean |
true if the host application handled the situation that process has
exited, otherwise, application will crash if render process crashed,
or be killed if render process was killed by the system. |
public void onSafeBrowsingHit (WebView view, WebResourceRequest request, int threatType, SafeBrowsingResponse callback)
Notify the host application that a loading URL has been flagged by Safe Browsing.
The application must invoke the callback to indicate the preferred response. The default
behavior is to show an interstitial to the user, with the reporting checkbox visible.
If the application needs to show its own custom interstitial UI, the callback can be invoked
asynchronously with SafeBrowsingResponse#backToSafety
or SafeBrowsingResponse.proceed(boolean)
, depending on user response.
Parameters | |
---|---|
view |
WebView : The WebView that hit the malicious resource. |
request |
WebResourceRequest : Object containing the details of the request. |
threatType |
int : The reason the resource was caught by Safe Browsing, corresponding to a
SAFE_BROWSING_THREAT_* value.
Value is SAFE_BROWSING_THREAT_UNKNOWN , SAFE_BROWSING_THREAT_MALWARE , SAFE_BROWSING_THREAT_PHISHING , SAFE_BROWSING_THREAT_UNWANTED_SOFTWARE , or SAFE_BROWSING_THREAT_BILLING |
callback |
SafeBrowsingResponse : Applications must invoke one of the callback methods. |
public void onScaleChanged (WebView view, float oldScale, float newScale)
Notify the host application that the scale applied to the WebView has changed.
Parameters | |
---|---|
view |
WebView : The WebView that is initiating the callback. |
oldScale |
float : The old scale factor |
newScale |
float : The new scale factor |
public void onTooManyRedirects (WebView view, Message cancelMsg, Message continueMsg)
This method is deprecated.
This method is no longer called. When the WebView encounters
a redirect loop, it will cancel the load.
Notify the host application that there have been an excessive number of HTTP redirects. As the host application if it would like to continue trying to load the resource. The default behavior is to send the cancel message.
Parameters | |
---|---|
view |
WebView : The WebView that is initiating the callback. |
cancelMsg |
Message : The message to send if the host wants to cancel |
continueMsg |
Message : The message to send if the host wants to continue |
public void onUnhandledKeyEvent (WebView view, KeyEvent event)
Notify the host application that a key was not handled by the WebView.
Except system keys, WebView always consumes the keys in the normal flow
or if shouldOverrideKeyEvent(WebView, KeyEvent)
returns true
. This is called asynchronously
from where the key is dispatched. It gives the host application a chance
to handle the unhandled key events.
Parameters | |
---|---|
view |
WebView : The WebView that is initiating the callback. |
event |
KeyEvent : The key event. |
public WebResourceResponse shouldInterceptRequest (WebView view, WebResourceRequest request)
Notify the host application of a resource request and allow the
application to return the data. If the return value is null
, the WebView
will continue to load the resource as usual. Otherwise, the return
response and data will be used.
This callback is invoked for a variety of URL schemes (e.g., http(s):
, data:
, file:
, etc.), not only those schemes which send requests over the network.
This is not called for javascript:
URLs, blob:
URLs, or for assets accessed
via file:///android_asset/
or file:///android_res/
URLs.
In the case of redirects, this is only called for the initial resource URL, not any subsequent redirect URLs.
Note: This method is called on a thread other than the UI thread so clients should exercise caution when accessing private data or the view system.
Note: When Safe Browsing is enabled, these URLs still undergo Safe
Browsing checks. If this is undesired, you can use WebView#setSafeBrowsingWhitelist
to skip Safe Browsing checks for that host or dismiss the warning in onSafeBrowsingHit(WebView, WebResourceRequest, int, SafeBrowsingResponse)
by calling SafeBrowsingResponse#proceed
.
Parameters | |
---|---|
view |
WebView : The WebView that is requesting the
resource. |
request |
WebResourceRequest : Object containing the details of the request. |
Returns | |
---|---|
WebResourceResponse |
A WebResourceResponse containing the
response information or null if the WebView should load the
resource itself. |
public WebResourceResponse shouldInterceptRequest (WebView view, String url)
This method is deprecated.
Use shouldInterceptRequest(WebView, WebResourceRequest)
instead.
Notify the host application of a resource request and allow the
application to return the data. If the return value is null
, the WebView
will continue to load the resource as usual. Otherwise, the return
response and data will be used.
This callback is invoked for a variety of URL schemes (e.g., http(s):
, data:
, file:
, etc.), not only those schemes which send requests over the network.
This is not called for javascript:
URLs, blob:
URLs, or for assets accessed
via file:///android_asset/
or file:///android_res/
URLs.
In the case of redirects, this is only called for the initial resource URL, not any subsequent redirect URLs.
Note: This method is called on a thread other than the UI thread so clients should exercise caution when accessing private data or the view system.
Note: When Safe Browsing is enabled, these URLs still undergo Safe
Browsing checks. If this is undesired, you can use WebView#setSafeBrowsingWhitelist
to skip Safe Browsing checks for that host or dismiss the warning in onSafeBrowsingHit(WebView, WebResourceRequest, int, SafeBrowsingResponse)
by calling SafeBrowsingResponse#proceed
.
Parameters | |
---|---|
view |
WebView : The WebView that is requesting the
resource. |
url |
String : The raw url of the resource. |
Returns | |
---|---|
WebResourceResponse |
A WebResourceResponse containing the
response information or null if the WebView should load the
resource itself. |
public boolean shouldOverrideKeyEvent (WebView view, KeyEvent event)
Give the host application a chance to handle the key event synchronously.
e.g. menu shortcut key events need to be filtered this way. If return
true, WebView will not handle the key event. If return false
, WebView
will always handle the key event, so none of the super in the view chain
will see the key event. The default behavior returns false
.
Parameters | |
---|---|
view |
WebView : The WebView that is initiating the callback. |
event |
KeyEvent : The key event. |
Returns | |
---|---|
boolean |
true if the host application wants to handle the key event
itself, otherwise return false |
public boolean shouldOverrideUrlLoading (WebView view, WebResourceRequest request)
Give the host application a chance to take control when a URL is about to be loaded in the
current WebView. If a WebViewClient is not provided, by default WebView will ask Activity
Manager to choose the proper handler for the URL. If a WebViewClient is provided, returning
true
causes the current WebView to abort loading the URL, while returning
false
causes the WebView to continue loading the URL as usual.
Note: Do not call WebView#loadUrl(String)
with the request's
URL and then return true
. This unnecessarily cancels the current load and starts a
new load with the same URL. The correct way to continue loading a given URL is to simply
return false
, without calling WebView#loadUrl(String)
.
Note: This method is not called for POST requests.
Note: This method may be called for subframes and with non-HTTP(S)
schemes; calling WebView#loadUrl(String)
with such a URL will fail.
Parameters | |
---|---|
view |
WebView : The WebView that is initiating the callback. |
request |
WebResourceRequest : Object containing the details of the request. |
Returns | |
---|---|
boolean |
true to cancel the current load, otherwise return false . |
public boolean shouldOverrideUrlLoading (WebView view, String url)
This method is deprecated.
Use shouldOverrideUrlLoading(WebView, WebResourceRequest)
instead.
Give the host application a chance to take control when a URL is about to be loaded in the
current WebView. If a WebViewClient is not provided, by default WebView will ask Activity
Manager to choose the proper handler for the URL. If a WebViewClient is provided, returning
true
causes the current WebView to abort loading the URL, while returning
false
causes the WebView to continue loading the URL as usual.
Note: Do not call WebView#loadUrl(String)
with the same
URL and then return true
. This unnecessarily cancels the current load and starts a
new load with the same URL. The correct way to continue loading a given URL is to simply
return false
, without calling WebView#loadUrl(String)
.
Note: This method is not called for POST requests.
Note: This method may be called for subframes and with non-HTTP(S)
schemes; calling WebView#loadUrl(String)
with such a URL will fail.
Parameters | |
---|---|
view |
WebView : The WebView that is initiating the callback. |
url |
String : The URL to be loaded. |
Returns | |
---|---|
boolean |
true to cancel the current load, otherwise return false . |