Button
Button
- Demonstration: Button and Fileupload
- Java API: Button
- JavaScript API: Button
- Style Guide: Button
Employment/Purpose
You could assign a label
and an image
to a button by the label
and image
properties. If both are specified, the dir
property control which is displayed up front, and the orient
property controls whether the layout is horizontal or vertical.
Within ZK 5, the file upload has been redesigned so it can be integrated with any widget. For example, the button now can be used to upload a file. In addition to this, the display of the upload status has been enhanced and can be customized easily.
Example
<button label="Left" image="/img/network.gif" width="125px"/>
<button label="Right" image="/img/network.gif" dir="reverse" width="125px"/>
<button label="Above" image="/img/network.gif" orient="vertical" width="125px"/>
<button label="Below" image="/img/network.gif" orient="vertical" dir="reverse" width="125px"/>
In addition to employing URLs to specify images, you can dynamically assign a generated image to a button using the setImageContent
method. Refer to the following section for details.
Tip: The setImageContent
method is supplied by all components that have an image
property. Simply put, setImageContent
is used for dynamically generated images, while image
is used for images identifiable by a URL.
File Upload
Any button[1] can be used to upload files. All you need to do is:
- Specify the
upload
attribute with true - Handles the
onUpload
event.
<button upload="true" label="Fileupload" onUpload="myProcessUpload(event.getMedia())"/>
When the file is uploaded, an instance of UploadEvent is sent to the button. Then, the event listener can retrieve the uploaded content by examining the return value of UploadEvent.getMedia().
- ↑ Any Toolbarbutton can be used to upload files too.
Custom Error Message When Fileupload Over Maxsize
1. Write your own AuLoader
package test;
import org.apache.commons.fileupload.FileUploadBase.SizeLimitExceededException;
import org.zkoss.zk.au.http.AuUploader;
public class MyUploader extends AuUploader {
protected String handleError(Throwable ex) {
if(ex instanceof SizeLimitExceededException){
SizeLimitExceededException e = (SizeLimitExceededException) ex;
return e.getActualSize() + " is over our limit";
}
return super.handleError(ex);
}
}
2. Apply it in the web.xml
<servlet>
<description>The asynchronous update engine for ZK</description>
<servlet-name>auEngine</servlet-name>
<servlet-class>org.zkoss.zk.au.http.DHtmlUpdateServlet</servlet-class>
<init-param>
<param-name>extension0</param-name>
<param-value>/upload=test.MyUploader</param-value>
</init-param>
</servlet>
- Result Video Demo
Limitation of the Default Mold
The default mold of a button uses HTML BUTTON tag to represent it visually. It is efficient, but it has some limitations:
- The look might be different from one browser to another.
- It doesn't support the file upload. In fact, it will become the trendy mold automatically if
upload
is specified. - If it is disabled it can not receive mouse events and hence can not use ZK popup component as tooltip.
If it is an issue, you could use the trendy mold instead.
<button label="OK" mold="trendy"/>
Configure to Use the Trendy Mold as Default
If you prefer to use the trendy mold as default, you could configure ZK by adding the following to /WEB-INF/zk.xml
<library-property>
<name>org.zkoss.zul.Button.mold</name>
<value>trendy</value>
</library-property>
File Download and browser processed links
Similar to file download link problem, if you specify href
to use a button for downloading, or if you are using a browser-processed link such as mailto:, tel:, or other similar user-processed instruction which would trigger a page unloading event, you also need to specify target
:
<button label="download" href="/myfile.pdf" target="_blank"/>
- If no specifying
target
, you will find event firing doesn't work anymore after you download a file.
Properties
Autodisable
Button.setAutodisable(String) is used to disable a button automatically, when it is clicked. It is useful to prevent the user from clicking it twice (and firing redundant requests), which is common if the request takes long to serve.
The simplest use is to specify it with self
as follows. Then, the button is disabled when it is clicked.
<button id="ok" label="OK" autodisable="self" />
If you'd like to disable several buttons, you could specify all of them in this property by separating with a comma. For example, the following disables both buttons, when one of them is clicked.
<button id="ok" label="OK" autodisable="ok,cancel" />
<button id="cancel" label="Cancel" autodisable="ok,cancel" />
The button will be enabled automatically, after the request has been served (i.e., the response has been sent back to the client). If you prefer to enable them manually (i.e., by calling Button.setDisabled(boolean) explicitly), you could prefix the ID with a plus (+
). For example,
<button id="ok" label="OK" autodisable="+self, +cancel" />
Then, you could enable them manually under the situation depending on your application's requirement, such as
if (something_happens) {
ok.setDisabled(false);
cancel.setDisabled(false);
}
Enable Autodisable for All Buttons
As described in ZK Developer's Reference: Customization, you could customize ZK to enable autodisable
for all button by specifying the following in the custom language addon:
<language-addon>
<component>
<component-name>button</component-name>
<extends>button</extends>
<property>
<property-name>autodisable</property-name>
<property-value>self</property-value>
</property>
</component>
</language-addon>
Href
In addition to handling the onClick event, you could specify the URL in the href property (Button.setHref(String)), such that the browser will navigate to the URL you specified directly (without sending back any request to the server). If you prefer to visit the URL in another browser window, you could specify the name in Button.setTarget(String) (just like using a HTML A tag).
Notice that the end user could hold the Control
key and click on the button to visit the link in a new browser window (like a HTML A tag does).
Href and the onClick Event
There are two ways to add behavior to a button
and toolbarbutton
. Firstly, you can specify a listener to the onClick
event. Secondly, you could specify a URL for the href
property (Button.setHref(String)). If both are specified, the href
property has the higher priority, i.e., the onClick event won't be sent.
<zk>
<window title="example">
<button label="click me" onClick="do_something_in_Java()"/>
<button label="don't click that one, click me" href="/another_page.zul"/>
</window>
</zk>
Href and SendRedirect
The href property is processed at the client. In other words, the browser will jump to the URL specified in the href property, so your application running at the server has no chance to process it.
If you have to process it at the server or you have to decide whether to jump to another URL based on certain condition, you could listen to the onClick event, process it, and then invoke Executions.sendRedirect(String) if it shall jump to another URL.
For end users, there is no difference between the use of Button.setHref(String) and Executions.sendRedirect(String).
<zk>
<window>
<button label="redirect" onClick="Executions.sendRedirect("another.zul")"/>
<button label="href" href="another.zul"/>
</window>
</zk>
Since the onClick event is sent to the server for processing, you are able to perform additional tasks before invoking Executions.sendRedirect(String), such as redirecting to another page only if certain conditions are satisfied.
On the other hand, the href
property is processed at the client side. Your application won't be notified when users click the button.
Type
Since 5.0.4
Button.setType(String) sets the button's type. It is designed to work with the HTML FORM tag. You rarely need it unless you want to work with HTML FORM and Servlets. For example,
<n:form action="/foo/my_handler" xmlns:n="native">
<textbox/>
<button type="submit" label="Submit"/>
<button type="reset" label="Reset"/>
</n:form>
Upload
By specifying the upload property (Button.setUpload(String)), you could make a button used for uploading files. For example,
<button label="Upload" upload="true" onUpload="handle(event.media)"/>
Once the file(s) are uploaded, the onUpload event will be sent with an instance of UploadEvent. And, you could retrieve the uploaded files from UploadEvent.getMedia() and UploadEvent.getMedias()
If you want to customize the handling of the file upload at the client, you can specify a JavaScript class when calling this method:
<button upload="foo.Upload"/> <!-- assume you implement a JavaScript class: foo.Upload -->
Options
Another options for the upload can be specified as follows:
<button label="Upload"
upload="true,maxsize=-1,multiple=true,accept=audio/*|video/*|image/*|MIME_type, native"/>
maxsize
: the maximal allowed upload size of the component, in kilobytes, or a negative value if no limit.native
: treating the uploaded file(s) as binary, i.e., not to convert it to image, audio or text files.multiple
: treating the file chooser allows multiple files to upload, the setting only works with HTML5 supported browsers (since ZK 6.0.0)accept
: specifies the MIME types of files that the server accepts, the setting only works with HTML5 supported browsers (since ZK 7.0.0). MIME type list.
Customize Upload Size Exceeding Message
Since 8.0.0 Please refer to ZK Developer's Reference/Internationalization.
For Example, (in WEB-INF/zk-label.properties)
MZul.2105=The request was rejected because its size ({0}) exceeds the configured maximum ({1})
Notice that you can change the index {0} & {1} to display different file size unit. (Auto:{0},{1} Byte:{2},{3} KB:{4},{5} MB:{6},{7})
Inherited Functions
Please refer to LabelImageElement for inherited functions.
Supported Events
onFocus |
Event: Event
Denotes when a component gets the focus. |
onBlur |
Event: Event
Denotes when a component loses the focus. |
onUpload |
Event: UploadEvent
Denotes user has uploaded a file to the component. |
- Inherited Supported Events: LabelImageElement
Supported Molds
Available molds of a component are defined in lang.xml embedded in zul.jar.
Supported Children
*NONE
Use Cases
Version | Description | Example Location |
---|---|---|
3.6 | Get dynamically generated Button reference in onClick Event | http://www.zkoss.org/forum/listComment/8780 |
3.6 | How to fire onClick Event on a Button | http://www.zkoss.org/forum/listComment/1716 |
Version History
Version | Date | Content |
---|---|---|
5.0.4 | August 2010 | Button.setType(String) was introduced to allow a button able to submit or reset a form.
<n:form action="a_uri" xmlns:n="native">
<button type="submit" label="Submit"/>
<button type="reset" label="Reset"/>
</n:form>
|
6.0.0 | December 2011 | Button.setUpload(String) the multiple setting was introduced to allow to choose multiple files to upload at the same time. (HTML5 supported browsers only)
<button upload="true,multiple=true" label="Fileupload"/>
|
7.0.0 | September 2013 | Button.setUpload(String) the accept setting was introduced to allow to specify the types of files that the server accepts. (HTML5 supported browsers only)
<button upload="true,accept=audio/*|video/*|image/*|MIME_type" label="Fileupload"/>
|