目录
Zend_ProgressBar is a component to create and update
progressbars in different environments. It consists of a single
backend, which outputs the progress through one of the multiple
adapters. On every update, it takes an absolute value and optionally
a status message, and then calls the adapter with some precalculated
values like percentage and estimated time left.
Zend_ProgressBar is quite easy in its usage. You
simply create a new instance of Zend_Progressbar, defining a
min- and a max-value, and choose an adapter to output the data. If
you want to process a file, you would do something like:
$progressBar = new Zend_ProgressBar($adapter, 0, $fileSize);
while (!feof($fp)) {
// Do something
$progressBar->update($currentByteCount);
}
$progressBar->finish();
In the first step, an instance of Zend_ProgressBar is
created, with a specific adapter, a min-value of 0 and a max-value
of the total filesize. Then a file is processed and in every loop
the progressbar is updated with the current byte count. At the end
of the loop, the progressbar status is set to finished.
You can also call the update() method of
Zend_ProgressBar without arguments, which just
recalculates ETA and notifies the adapter. This is useful when there
is no data update but you want the progressbar to be updated.
If you want the progressbar to be persistent over multiple requests,
you can give the name of a session namespace as fourth argument
to the constructor. In that case, the progressbar will not notify
the adapter within the constructor, but only when you call
update() or finish(). Also the current
value, the status text and the start time for ETA calculation will
be fetched in the next request run again.
Zend_ProgressBar comes with the following three adapters:
Zend_ProgressBar_Adapter_Console is a text-based adapter
for terminals. It can automatically detect terminal widths but supports
custom widths as well. You can define which elements are displayed with
the progressbar and as well customize the order of them. You can also
define the style of the progressbar itself.
![[注意]](images/note.png) |
Automatic console width recognition |
|---|---|
|
You can set the adapter options either via the set* methods
or give an array or a Zend_Config instance with options as first
parameter to the constructor. The available options are:
width: Either an integer or theAUTOconstant ofZend_Console_ProgressBar.-
elements: EitherNULLfor default or an array with at least one of the following constants ofZend_Console_ProgressBaras value:ELEMENT_PERCENT: The current value in percent.ELEMENT_BAR: The visual bar which display the percentage.ELEMENT_ETA: The automatic calculated ETA. This element is firstly displayed after five seconds, because in this time, it is not able to calculate accurate results.ELEMENT_TEXT: An optional status message about the current process.
textWidth: Width in characters of theELEMENT_TEXTelement. Default is 20.barLeftChar: A string which is used left-hand of the indicator in the progressbar.barRightChar: A string which is used right-hand of the indicator in the progressbar.barIndicatorChar: A string which is used for the indicator in the progressbar. This one can be empty.
Zend_ProgressBar_Adapter_JsPush is an adapter which let's
you update a progressbar in a browser via Javascript Push. This means
that no second connection is required to gather the status about a
running process, but that the process itself sends its status directly
to the browser.
You can set the adapter options either via the set* methods
or give an array or a Zend_Config instance with options as first
parameter to the constructor. The available options are:
updateMethodName: The javascript method which should be called on every update. Default value isZend_ProgressBar_Update.finishMethodName: The javascript method which should be called after finish status was set. Default value isNULL, which means nothing is done.
The usage of this adapter is quite simple. First you create a progressbar
in your browser, either with JavaScript or previously created with plain
HTML. Then you define the update method and optionally the finish method
in JavaScript, both taking a json object as single argument. Then you
call a webpage with the long-running process in a hidden
iframe or object tag. While the process is
running, the adapter will call the update method on every update with
a json object, containing the following parameters:
current: The current absolute valuemax: The max absolute valuepercent: The calculated percentagetimeTaken: The time how long the process ran yettimeRemaining: The expected time for the process to finishtext: The optional status message, if given
例 38.1. Basic example for the client-side stuff
This example illustrates a basic setup of HTML, CSS and JavaScript for the JsPush adapter
<div id="zend-progressbar-container">
<div id="zend-progressbar-done"></div>
</div>
<iframe src="long-running-process.php" id="long-running-process"></iframe>
#long-running-process {
position: absolute;
left: -100px;
top: -100px;
width: 1px;
height: 1px;
}
#zend-progressbar-container {
width: 100px;
height: 30px;
border: 1px solid #000000;
background-color: #ffffff;
}
#zend-progressbar-done {
width: 0;
height: 30px;
background-color: #000000;
}
function Zend_ProgressBar_Update(data)
{
document.getElementById('zend-progressbar-done').style.width = data.percent + '%';
}
This will create a simple container with a black border and a
block which indicates the current process. You should not hide
the iframe or object by display: none;,
as some browsers like Safari 2 will not load the actual content then.
Instead of creating your custom progressbar, you may want to use one of the available JavaScript libraries like Dojo, jQuery etc. For example, there are:
|
Interval of updates |
|---|---|
You should take care of not sending too many updates, as every update has a min-size of 1kb. This is a requirement for the Safari browser to actually render and execute the function call. Internet Explorer has a similar limitation of 256 bytes. |
Zend_ProgressBar_Adapter_JsPull is the opposite of jsPush,
as it requires to pull for new updates, instead of pushing updates out
to the browsers. Generally you should use the adapter with the
persistence option of the Zend_ProgressBar. On notify,
the adapter sends a JSON string to the browser, which looks exactly
like the JSON string which is send by the jsPush adapter. The only
difference is, that it contains an additional parameter,
finished, which is either false when
update() is called or true, when
finish() is called.
You can set the adapter options either via the set* methods
or give an array or a Zend_Config instance with options as first
parameter to the constructor. The available options are:
exitAfterSend: Exits the current request after the data were send to the browser. Default istrue.