I'm designing a news-reading app and using the NavigateToString() of a webbrowser to show some string. Now I want to implement the off-line reading function, the html string had already been downloaded, except the image.
Windows phone has implemented the image-cache function, once the Image is requested, it had been cached. But now problem is that, all the html strings are stored in a array, some of those html strings hadn't been shown throught the navigateToString(), namely the imgs in those string couldn't show up if the internet is disconnected.
So I'm wondering how to cache the imgs in the webbrowser?
thanks,
ellic
It ain't gonna be easy or pretty.
Here's one thing you can do...
Parse the HTML using something like the HtmlAgilityPack. Linq should be a good solution for finding all the images. If you want to use xpath, you can do that too.
Find all Images in the HTML and use a WebClient (or better yet, a WebRequest) to fetch them.
Save them as part of your database that you use to store your HTML strings (say, Base64 encoded if your medium needs to be strings, key'ed by the URI to the image);
When you want to display the offline HTML, again, parse the HTML and replace all references to images with the data protocol equivalent of your cached images.
Related
I am reluctant to post this, but I am having trouble understanding how markdown actually "saves" to a database.
When I'm creating a migration, I will add columns and specify the type of value (i.e. integer, text, string, etc.) and in the course of operation on the website, users will input different information that is then saved in the DB. No problem there.
I just can't seem to wrap my head around the process for markdown. I've read about saving the HTML or saving the markdown file, rendering at runtime, pros and cons all that.
So, say I use an editor like Tiny MCE which attaches itself to a textarea. When I click "Submit" on the form, how does that operate? How does validation work? Feel free to answer my question directly or offer some resource to help further my understanding. I have an app built on Laravel so I'm guessing I'll need to use a package like https://github.com/GrahamCampbell/Laravel-Markdown along with an editor (i.e. Tiny MCE).
Thanks!
Let's start with a more basic example: StackOverflow. When you are writing/editing a question or answer, you are typing Markdown text into a textarea field. And below that textarea is a preview, which displays the Markdown text converted to HTML.
The way this works (simplified a little) is that StackOverflow uses a JavaScript library to parse the Markdown into HTML. This parsing happens entirely client side (in the browser) and nothing is sent to the server. With each key press in the textarea the preview is updated quickly because there is no back-and-forth with the server.
However, when you submit your question/answer, the HTML in the preview is discarded and the Markdown text from the textarea is forwarded to the StackOverflow server where is is saved to the database. At some point the server also converts the Markdown to HTML so that when another user comes alone and requests to view that question/answer, the document is sent to the user as HTML by the server. I say "at some point" because this is where you have to decide when the conversion happens. You have two options:
If the server converts the HTML when is saves it to the Database, then it will save to two columns, one for the Markdown and one of for the HTML. Later, when a user requests to view the document, the HTML document will be retrieved from the database and returned to the user. However, if a user requests to edit the document, then the Markdown document will be retrieved from the database and returned to the user so that she can edit it.
If the server only stores the Markdown text to the database, then when a user requests to view the document, the Markdown document will be retrieved from the database, converted to HTML and then returned to the user. However, if a user requests to edit the document, then the Markdown document will be retrieved from the database and returned to the user (skipping the conversion step) so that she can edit it.
Note that in either option, the server is doing the conversion to HTML. The only time the conversion happens client-side (in the browser) is for preview. But the "preview" conversion is not used to display the document outside of edit mode or to store the document in the database.
The only difference between something like StackOverflow and TinyMCE is that in TinyMCE the preview is also the editor. Behind the scenes the same process is still happening and when you submit, it is the Markdown which is sent to the server. The HTML used for preview is still discarded.
The primary concern when implementing such a system is that if the Markdown implementation used for preview is dissimilar from the implementation used by the server, the preview may not be very accurate. Therefore, it is generally best to choose two implementations that are very similar or, if available, use the same implementations for both.
It is actually very simple.
Historally, in forums, there used be BBCodes, which are basically pseudo-tags that allow you to format your text in some say. For example [b][/b] used to mean "make this text bold". In Markdown, it happens the exact same thing, but with other characters like *text* or **text**.
This happens so that you only allow your users to use a specific formatting, otherwise if you'd allow to write pure HTML, XSS (cross-site scripting) issues would arise and it's not really a good idea.
You should then save the HTML on the database. You can use, for example, markdown-js which is a Markdown parser that parses Markdown to HTML.
I have seen TinyMCE does not make use of Markdown by default, since it's simple a WYSIWYG editor, however it seems like it also supports a markdown-like formatting.
Laravel-Markdown is a server-side markdown render helper, you can use this on Laravel Blade views. markdown-js is instead client-side, it can be used, for example, to show a preview of what you're writing in real-time.
I would like to send a lot of data through ajax request to my server which will generate pdf or jpg format according to that data.
Now i have done all that, my issue is to how output that generated pdf/jpg back to the user trough ajax? I guess i might be able to use json for that, but im not really sure how, and i think there would be a lot issues with pdf.
Also if some one gonna suggest using form with hidden inputs that will not work since i have really big multidimensional array with lot's of data and it would simply take to much effort to make it work.
By the way, i am using jquery, but anything else is acceptable as long as it does the job done without making me to rewrite half of my script.
To display a JPG
AJAX: You can return the data hex encoded (be sure to set the content type appropriately: header('Content-type: image/jpeg')). Then you just inject an <img/> element into the DOM and set it's src attribute to the returned Data URI.
HTML: Also, you could inject the <img/>'s with a normal src URL to some location on your server.
For PDF
It's a little more tricky. Some browsers display PDF's natively (Chrome/Firefox), others rely on optional third-party plugins. You can detect these plugins, but can't control whether the PDF is displayed in a window/frame or is downloaded.
If you choose to display, you can create a new window/tab to display it or display it in an iframe dynamically.
I want to design a web album with every image in the album having it's own title, and description. So, at a time only one set of image, title and description would be visible. And on clicking next button, the next set of image, title and description would appear,and so on.
So am wondering, what would be the best way to design with? HTML or AJAX?
I don't want to use the ready to use tools such as lightbox.
Do you want the browser's back button to work? If so, then you should make your life simple
and use html (since you will only be displaying one image at a time either way).
Ajax implies using html. On the other hand, using html does not necessarily imply that you need to use AJAX to load content dynamically.
What is the purpose of this project? If you are doing it for the learning experience you should go on with AJAX (from scratch). If you want speed and quality use an existing web image gallery. If you need to write it yourself use plain html (or an ajax framework such as dojo, jquery, etc. this will save you a lot of pain solving cross-browser quirks).
In addition, if you want to be able to click a button to take you to the next (previous) image
and you don't know how many images you will have beforehand, then you are looking for dynamic behavior. You can code dynamic logic either on the client side (javascript), or on the server side (let's say "php" to start with).
Also, how do you plan to keep the corresponding (image, title, description) together?
If you only have a 3 images, say you could hard code each of this into its corresponding html file. eg. 1.html, 2.html, 3.html. Then you would have to point the forward button from a.html to point to b.html. etc...
If you didn't want this boring static behavior and wanted something smarter, say you decided for AJAX. Then you would only have 1.html file and from there (using javascript) you would ask your server for the (image, title, description) and load all that (dynamically, without refreshing the browser) into the same page. The easiest way to get this from the sever is by just reading a a static (XML, or JSON) file which contains all the info (image urls, titles, descriptions). Then with javascript and using DOM manipulation you would remove the old image, and add the new one.
However, this would all be a lot simpler with server-side processing (and it's worth learning). In this case you could have a url which takes a parameter with the image number. eg. http://example.com/gallery/index.php?image=X
then before the server responds to the client with the html, it would realize that you want to load image X so it would get it's corresponding description, title, and url. and "embed" those into the file. Of course, depending on the number, it would also add the right links for the previous and next buttons. Eg. If the currently displaying image was 9 then forward button would "dynamically" be determined to link to (X+1) : http://example.com/gallery/index.php?image=10
Not sure if what I want to do is possible, but what I am hoping to do is somehow gather certain pieces of text from a website, remove the header, footer, background, all formatting, and place it into my application in a scrollview or something similar...
I'll give you an example... Imagine I was making wikipedia's iPhone app, I want to download the information about the wiki on dogs, without the header, side bars etc, just the text. How would I go about doing this?
I understand that for this I have not provided any example code or what I've tried or started, but that's just because in this case I'm lost! That doesn't mean I want full chunks of code either. Any help will do. If this doesn't work, I will just have to make a 'mobile optimised' version of the webpages I want to include in my app.
Thanks
(Edit: the term I was trying to use was 'strip the web page of its HTML coding')
You may be going about this the wrong way, or perhaps even asking the wrong question.
Does the target website have an API or datafeed of some kind?
Can you get the information you need in JSON or XML format directly from the site?
I think you've misunderstood the technology. HTML is merely the framwork on which the formatting and data is hung.
Parsing the HTML page seems like an awfully big headache, I doubt you'll ever be able to get it to work, because almost all sites these days are partially or wholly generated on the server side, the page is only the result.
Some sites hide the information in memory and others get it dynamically through ajax for example, which means that simply trying to get the data by parsing the HTML will get zero data.
Another issue you should be aware of though, is that simply copying the data from generated websites may open yourself up to copyright issues.
You have to parse the html code and search for the part that you want and "throw" away the part that you do not need. This is more or less like bruteforcing and the code of the website should not change otherwise you are screwed. So you have to write the parser by hand with this method. But maybe there is a atom or rss feed and you can parse this one. This will be much more easier and you are not depending on the website layout because the rss/atom feed is just about the data. For parsing rss you could try out NSXMLParser.
And then you have to make a valid html page out of the data and present it in the UIWebView
I know this question might sound a little bit crazy, but I tough that maybe someone could come up with a smart idea:
Imagine you have 1000 thumbnail images on a single HTML page.
The image size is about 5-10 kb.
Is there a way to load all images in a single request? Somehow zip all images into a single file…
Or do you have any other suggestions in the subject?
Other options I already know of:
CSS sprites
Lazy load
Set Expire headers
Downloads images across different hostnames
There are only two other options I can think of given your situation:
Use the "data:" protocol and echo a base64 encoded version of your thumbnails directly into the HTML page. I would not recommend this since you cannot then cache those images on the users browser.
Use HTML5's Web Storage to store all the images as records with the base64 encoded image data stored as BLOBs in a column. Once the database has downloaded to the users machine, use Javascript to loop through all the records and create the thumbnails on the page dynamically using something like jQuery. With this option you would need to wait till the entire database was done downloading on the end users browser, and they will need a fairly modern browser.
I think your best bet is a combination of lazy loading, caching with expires headers and serving images from multiple hostnames.
If the images can be grouped logically, CSS sprites may also work for you in addition to everything above. For example, if your thumbnails are for images uploaded on a certain day...you may be able to create a single file for each day which could then be cached on the users browser.
This is done by using what's called a CSS sprite; a single image with all the other images inside it, with the particular part that's wanted in the html selected by css.
See one tutorial at http://css-tricks.com/css-sprites
It sounds like you want something like SPDY's server push. When the client requests the HTML page (or the first image), SPDY allows the server to push the other resources without waiting for more requests.
Of course, this is still experimental.
You could try the montage command of imagemagick to create a single image.