I use MvxImageViewLoader for MvvmCross Xamarin applications.
This component is really great and simplifies the images loading pretty much, but it (at least, out-of-the-box) is pretty basic and most of modern applications require some reacher functionality, for instance, loading/progress images or images nice appearing/transitions (possibly with custom animation).
I see there is DefaultImagePath property, but that's static image, which I can probably use by default, but that's not animated view or something.
So, is there any way to customize/extend the loader behaviour (for default image appearing, images transition (from default to loaded)) etc?
And also I've noticed that the loader caches the image and even if I trigger bound property changing (leaving the image url the same) it does not refresh the image. I guess, "caching" really means caching and so on, but what if I need to change the user icon or something... how can I forse the cache refreshing with the image loader?
Thank you!
So, is there any way to customize/extend the loader behaviour (for default image appearing, images transition (from default to loaded)) etc?
No - advanced features like fade-in/fade-out/animated-placeholder display aren't supported within the standard MvvmCross image view, and no-one that I know of has provided any samples or tutorials about how this can be done.
For adding such functionality, you can use normal software techniques - inheritance, aggregation and cut, copy, paste. e.g. you could simply create your own AgatImageView which had the behaviour your app requires based on MvxImageView.cs.
Some examples of creating your own data-bound controls is given in N=18 and N-19 of http://mvvmcross.wordpress.com/
As you already mentioned in upper comments you may use default iOS' UIActivityIndicatorView for showing progress and you should hide the progress in afterImageChangeAction, you can check if UIImageView.Image field is not null, to make sure that the image is loaded.
Regarding the caching, it's not that easy here. By default MvxImageViewLoader relies on MvvmCross framework's implementation of IMvxFileDownloadCache interface. This interface has only one public method RequestLocalFilePath(), so even if you get an instance from IoC container (Mvx.Resolve()) you won't be able to clean-up the existing cache (to do that you need to reset private _entriesByHttpUrl field of MvxFileDownloadCache class).
If you really need this, you have to copy-paste existing MvxFileDownloadCache class and make your tweaks. But I am not sure about your use-cases where you need this. If you download images from the web, the URL of the image is a sort of a key in the cache, so if you need to reload just change the URL.
Maybe you could use some old-school approach like adding GET parameters to the URL: http://mydomain.com/images/myimage.jpg?timestamp=123456. Usually this helps everywhere :-). Although I didn't test it with MvxImageViewLoader, it's just my best guess.
Related
I want to show a scroll view that has fairly large number of thumbnails. eg: https://cdn.vox-cdn.com/thumbor/sddJ5KHoGDbZfx8jcNey4iahmu0=/0x0:1395x1171/1200x800/filters:focal(587x475:809x697)/cdn.vox-cdn.com/uploads/chorus_image/image/57064313/Screen_Shot_2015-09-07_at_9.11.34_AM.0.0.png
I want to load the view as fast as possible without delaying it until all images are loaded. This essentially means I need to lazy load image content. While each image is downloaded, a placeholder image (fetched locally) should be shown. I certainly know how to do this from scratch, but wanted to know if there are standard solutions available. Can I setup Xamarin.Forms.Image class to get this behavior?
Is there any particular reason for which you want to use a ScrollView specifically ?
From what you're describing, it looks like you should actually be working with a ListView instead (which will improve performance by a LOT if you have a large list of images).
Then, like #SushiHangover said, there is FFImageLoading that can help you work with these images, or you can create you own Image class, to implement a custom solution on both android and iOS.
Glide is a faily easy to use solution for Android, and SDWebImage is also a good solution for iOS.
So I've been creating a custom responsive theme in Wordpress and I've hit a wall when it comes to image management. I'd like to style images in a way that wordpress doesn't seem to inherently support - I'm looking for something like this:
with the images added via the regular wordpress media management pane, and inserted into posts/pages. The images should be out of the flow of the content but accurately placed next to the correct headers/text blocks. Most importantly, the images ought to collapse into a column with the rest of the content at the correct media query breakpoints.
Here's what I've tried, from worst to best:
Hard coded images in template files
Obviously the worst option. Not portable, requires a lot of meddling, and would be almost impossible to align the images with the correct content. Also, no real way of making the images responsive with the content.
Use the default image styling and abandon the idea of pulling the images out of the regular flow
Non optimal, but it would allow anyone to change/edit images easily.
Remove images from the results of the_content(), then place and style them separate.
Portable, but has the same problems as #1 - difficult to align the images with content and keep responsiveness.
Use the featured image on pages that only require one image
Pretty good option for pages that need ONLY one image, but there is no easy way to make the featured image an arbitrary size/aspect ratio.
Use markup in the editor to correctly layout the images
Requires anyone editing the posts/pages to have some knowledge of the underlying theme. This seems to work the best, but it isn't portable (might break stuff on theme change).
While I've had the best results with this option, it seems sort of antithetical to using a cms/wysiwyg editor in the first place.
My question is whether or not the last option really is the best to get the result I want?
In the end, the answer was clearly custom fields, and none of the other options I listed. With the advanced custom fields plugin, it becomes a breeze to do what I wanted. You don't need the plugin, but it makes image management a whole lot easier, as it fully integrates the wordpress media library with the custom field (which you would have to do manually otherwise). With the plugin, custom fields meet all of my needs (responsiveness, portability, and ease of use for the technically challenged).
The image component allows Free Ratio cropping out of the box. I'm a bit baffled at why there is no Aspect Ratio option (keeping height and width constrained to each other), which would work much better for us. Is this an existing feature that can be enabled, or a custom task in Java?
I am using CQ 5.4.
This is OOTB since 5.4 (atleast), though not well documented.. Set up your smart image widget like so:
<image-16x10
jcr:primaryType="cq:Widget"
allowFileReference="{Boolean}true"
cropParameter="./image-16x10/imageCrop"
fileReferenceParameter="fileReference"
name="./image-16x10/file"
requestSuffix=".img.png"
rotateParameter=""
title="16x10"
xtype="html5smartimage">
<cropConfig
jcr:primaryType="nt:unstructured">
<aspectRatios
jcr:primaryType="nt:unstructured">
<aspectRatio-16x10
jcr:primaryType="nt:unstructured"
text="16x10"
value="16,10"/>
</aspectRatios>
</cropConfig>
</image-16x10>
The cropConfig node structure is what youre interested in. text="16x:10" is what will appear in the Crop dropdown, value="16,10" is the actual fixed Crop size for the tool. You can add as many predefined crops you want per html5smartimage widget.
The image-16x10 and aspectRatio-16x10 names aren't required, but not a useful convention to help in maintainability of the config.If you allow multiple aspectRatios then the image-16x10 naming probably doesnt make as much sense tho its not a bad idea to provide semantic naming to your aspectRatio definition node.
If you'd like to generate images with different aspectRatios, try this...
http://experience-aem.blogspot.com/2013/09/cq-image-custom-aspect-ratios-crop.html
The crop parameters are saved in different properties and not "cropParameter" of the html5smartimage widget
That would be a custom JavaScript widget: the one you're using (smart image) does not have an aspect ratio functionality (or just I never seen one), even in 5.6.
You could extend the existing widget, and provide this functionality in your own, using Javascript though -- it's not trivial, but not rocket science either -- see source code for smart image to see how it extends smart panel, and then registers itself into the framework.
I've been looking around to see if there exists a good way to prevent viewers from using their right click options to download images that I upload to my website.
I know that people can look at the image url in the page source, and was wondering if you suggest a way to prevent them being taken, by disabling the save image option.
This is an unsolvable problem.
As long as you actually want people to see the images, you cannot prevent them from saving them via a number of methods (e.g. screenshots). All measures you might think of will just annoy your users, without actually preventing them from doing what they want anyway. Also consider that the people watching those images will have some interest in them (otherwise they would not watch them in the first place), so there we already have a motive for them to keep a copy.
The only way to reliably prevent people from saving the images is to never let them copy them onto their computers in the first place (and remember: showing something on another computer always entails making a copy).
One solution could be to invite people into a place where they can view the image on a screen which you control, and not let them take any pictures. Think of modern cinemas where security people with night sights watch the spectators and pull out those who might have been handling any camera like device.
If you want to make it even more difficult, do not use an IMG tag. Instead, define the image using CSS with the property 'background-image'. To make it even more tricky, define that property at runtime using JavaScript that was placed on the page using base64 encoding.
You can try this...
onload=function(){
document.oncontextmenu=function(){return false;}
}
This will disallow the operation of the context (right mouse button click) menu...
If a user knows what they're doing they can get around this, though.
I suggest not doing this. It's annoying and you're not actually protecting yourself.
If you must, jQuery makes it pretty easy to disable the right click menu:
$(document).ready(function(){
$('img').bind("contextmenu",function(){
return false;
});
});
Just make your images so ugly no one would want to take them.
Seriously, what are you worried about?
If you use the Microsoft Ajax Seadragon Deep Zoom viewer for you images then you can present your images as lots of overlapping tiles - a real pain to stick back together, difficulty depends on images size, but for hi-resolution images it makes 'printscreen' the only option for those wanting to steal stuff.
Incidentally the contextmenu thing works on divs better than images (things bubble) and you don't have to offend people by doing no click on the whole document.
To do it by class, e.g. with Prototype:
$$('.your-image-container-class').each(function(s) {s.oncontextmenu=function(){return false;}});
Is there some standard way to make my applications skinnable?
By "skinnable" I mean the ability of the application to support multiple skins.
I am not targeting any particular platform here. Just want to know if there are any general guidelines for making applications skinnable.
It looks like skinning web applications is relatively easy. What about desktop applications?
Skins are just Yet Another Level Of Abstraction (YALOA!).
If you read up on the MVC design pattern then you'll understand many of the principles needed.
The presentation layer (or skin) only has to do a few things:
Show the interface
When certain actions are taken (clicking, entering text in a box, etc) then it triggers actions
It has to receive notices from the model and controller when it needs to change
In a normal program this abstraction is done by having code which connects the text boxes to the methods and objects they are related to, and having code which changes the display based on the program commands.
If you want to add skinning you need to take that ability and make it so that can be done without compiling the code again.
Check out, for instance, XUL and see how it's done there. You'll find a lot of skinning projects use XML to describe the various 'faces' of the skin (it playing music, or organizing the library for an MP3 player skin), and then where each control is located and what data and methods it should be attached to in the program.
It can seem hard until you do it, then you realize it's just like any other level of abstraction you've dealt with before (from a program with gotos, to control structures, to functions, to structures, to classes and objects, to JIT compilers, etc).
The initial learning curve isn't trivial, but do a few projects and you'll find it's not hard.
-Adam
Keep all your styles in a separate CSS file(s)
Stay away from any inline styling
It really depends on how "skinnable" you want your apps to be. Letting the user configure colors and images is going to be a lot easier than letting them hide/remove components or even write their own components.
For most cases, you can probably get away with writing some kind of Resource Provider that serves up colors and images instead of hardcoding them in your source file. So, this:
Color backgroundColor = Color.BLUE;
Would become something like:
Color backgroundColor = ResourceManager.getColor("form.background");
Then, all you have to do is change the mappings in your ResourceManager class and all clients will be consistent. If you want to do this in real-time, changing any of the ResourceManager's mappings will probably send out an event to its clients and notify them that something has changed. Then the clients can redraw their components if they want to.
Implementation varies by platform, but here are a few general cross-platform considerations:
It is good to have an established overall layout into which visual elements can be "plugged." It's harder (but still possible) to support completely different general layouts through skinning.
Develop a well-documented naming convention for the assets (images, HTML fragments, etc.) that comprise a skin.
Design a clean way to "discover" existing skins and add new ones. For example: Winamp uses a ZIP file format to store all the images for its skins. All the skin files reside in a well-known folder off the application folder.
Be aware of scaling issues. Not everyone uses the same screen resolution.
Are you going to allow third-party skin development? This will affect your design.
Architecturally, the Model-View-Controller pattern lends itself to skinning.
These are just a few things to be aware of. Your implementation will vary between web and fat client, and by your feature requirements. HTH.
The basic principle is that used by CSS in web pages.
Rather than ever specifying the formatting (colour / font / layout[to some extent]) of your content, you simply describe what kind of content it is.
To give a web example, in the content for a blog page you might mark different sections as being an:
Title
Blog Entry
Archive Pane
etc.
The Entry might be made of severl subsections such as "heading", "body" and "timestamp".
Then, elsewhere you have a stylesheet which specifies all the properties of each kind of element, size, alignment, colour, background, font etc. When rendering the page or srawing / initialising the componatns in your UI you always consult the current stylesheet to look up these properties.
Then, skinning, and indeed editing your design, becomes MUCH easier. You simple create a different stylesheet and tweak the values to your heat's content.
Edit:
One key point to remember is the distinction between a general style (like classes in CSS) and a specific style (like ID's in CSS). You want to be able to uniquely identify some items in your layout, such as the heading, as being a single identifiable item that you can apply a unique style to, whereas other items (such as an entry in a blog, or a field in a database view) will all want to have the same style.
It's different for each platform/technology.
For WPF, take a look at what Josh Smith calls structural skinning: http://www.codeproject.com/KB/WPF/podder2.aspx
This should be relatively easy, follow these steps:
Strip out all styling for your entire web application or website
Use css to change the way your app looks.
For more information visit css zen garden for ideas.
You shouldn't. Or at least you should ask yourself if it's really the right decision.
Skinning breaks the UI design guidelines. It "jars" the user because your skinned app operates and looks totally different from all the other apps their using. Things like command shortcut keys won't be consistent and they'll lose productivity. It will be less handicapped accessible because screen readers will have a harder time understanding it.
There are a ton of reasons NOT to skin. If you just want to make your application visually distinct, that's a poor reason in my opinion. You will make your app harder to use and less likely that people will ever go beyond the trial period.
Having said all that, there are some classes of apps where skinning is basically expected, such as media players and imersive full screen games. But if your app isn't in a class where skinning is largely mandated, I would seriously consider finding other ways to make your app better than your competition.
Depending on how deep you wish to dig, you can opt to use a 'formatting' framework (e.g. Java's PLAF, the web's CSS), or an entirely decoupled multiple tier architecture.
If you want to define a pluggable skin, you need to consider that from the very beginning. The presentation layer knows nothing about the business logic but it's API and vice versa.
It seems most of the people here refer to CSS, as if its the only skinning option.
Windows Media Player (and Winamp, AFAIR) use XML as well as images (if neccesary) to define a skin.
The XML references hooks, events, etc. and handles how things look and react. I'm not sure about how they handle the back end, but loading a given skin is really as simply as locating the appropriate XML file, loading the images then placing them where they need to go.
XML also gives you far more control over what you can do (i.e. create new components, change component sizes, etc.).
XML combined with CSS could give wonderful results for a skinning engine of a desktop or web application.