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Message #00245
Re: [Ubuntu-phone] [Core-Apps] Solution for offline image using pure qml
It should still be filed as a bug in Launchpad, since that's how we
track things that need to be done, even feature requests.
Michael Hall
mhall119@xxxxxxxxxx
On 03/28/2013 11:24 AM, Joey Chan wrote:
> This isn't a bug of SDK, but a necessary plugin for development. Some
> functions should be implemented with C++, and these functions can be
> included in "Ubuntu.Component 0.x",
>
> for example:
> import Ubuntu.Component.native 0.1 as UCore // all common
> functions implemented in this plugin, should done by Canonical
>
> function saveImage ()
> {
> UCore.saveImage(url) ;
> }
>
> function loadImage ()
> {
> return UCore.loadImage(url) ;
> }
>
>
>
> 2013/3/28 Matthias Gehre <gehre.matthias@xxxxxxxxx
> <mailto:gehre.matthias@xxxxxxxxx>>
>
> I guess we should fill a bug against ubuntu-sdk then?
>
>
> 2013/3/28 Roman Shchekin <mrqtros@xxxxxxxxx <mailto:mrqtros@xxxxxxxxx>>
>
> I agree with Joey - this functionality should be implemented by
> Canonical, because not only RSS Reader team need it.
>
>
> 2013/3/28 Joey Chan <qqworini@xxxxxxxxx <mailto:qqworini@xxxxxxxxx>>
>
> Hi Matthias,
>
> Agree with your solution, and other solutions include
> "homepath" or QnetworkManager are welcome. All these mean
> that we can't store any images without C++, so I suggest
> developers from Canonical could create some qml plugins for
> functions which can't be implemented with pure qml.
>
> :)
>
>
> 2013/3/28 Matthias Gehre <mgehre@xxxxxxxxxxxxxxxxxx
> <mailto:mgehre@xxxxxxxxxxxxxxxxxx>>
>
> I "solved" this problem in whosthere by
> subclassingQQuickImageProvider, but that needs some C++
> code to be written.
> See https://github.com/mgehre/whosthere/blob/master
> imageprovider.h/cpp
>
>
> 2013/3/28 Joey Chan <qqworini@xxxxxxxxx
> <mailto:qqworini@xxxxxxxxx>>
>
> yep, a common plugin is necessary
>
>
> 2013/3/28 <mrqtros@xxxxxxxxx <mailto:mrqtros@xxxxxxxxx>>
>
> Other teams need this ability too, so it is must
> be included in sdk and used this way:
>
> // qml code
>
> Ubuntu.saveImageToLocalStorage(...)
>
> ...
>
> Ubuntu.loadImageFromLocalStorage(...)
>
>
> Or something like that =)))
>
>
> 27.03.13 13:39 Joey Chan написал(а):
>
> Hi Ladies and Gentlemen,
>
> I'm here to discuss about the "offline image
> using pure qml", which means, If images are from
> remote server, we developers need to download
> them to local file system so that apps can load
> images without Internet connections.
>
> solution 1 ( failed )
>
> this solution use xmlhttprequest to download the
> whole image data, convert it to base64 string
> then show it to "Image"
>
> source code:
> var xhr = new XMLHttpRequest();
> xhr.overrideMimeType('text/plain;
> charset=x-user-defined'); // doesn't work in
> qml but html
> xhr.open("GET", "http://www.xxx.com/xxx.png";);
> xhr.onreadystatechange = function() {
> if (xhr.readyState === 4) {
> var blob = xhr.responseText ;
> var blobarray = new Array ;
> for (var i = 0, len =
> blob.length; i < len; ++i) {
>
> blobarray.push(blob.charCodeAt(i) & 0xff );
> }
> // then use Image.source =
> "data:image/png;base64," + blobarray.join("")
> to show the image
>
> }
> };
> xhr.send();
>
> This snippet shows an old way to download binary
> data using xmlhttprequest level 1, but not work
> in qml ( overrideMimeType not supported ) .
> Also, xmlhttprequest level 2 (support binary
> data) not supported by qml 2.0
>
> Conclusion: it's better update the
> xmlhttprequest to level 2
>
>
> solution 2: (success but not perfect)
>
> This solution use qml2 canvas to load a remote
> url then save it to local file system.
>
> source code:
> property string url: "http://www.xxx.com/xxx.png";
> Canvas {
> id: mycanvas
> y: 350
> width: 200
> height: 200
>
> Component.onCompleted:
> {
> mycanvas.loadImage(url);
> }
>
> onImageLoaded:
> {
> console.log("onImageLoaded");
> requestPaint();
> }
>
> onPaint: {
> var ctx = mycanvas.getContext("2d");
>
>
> ctx.drawImage(url, 0, 0);
> ctx.restore();
>
>
> }
> }
>
> MouseArea
> {
> anchors.fill: parent
> onClicked: mycanvas.save("./aaa.png");
> }
>
>
> This solution can download every image, but, the
> final function "save" can't support "homepath"
> and "temppath", which means, we don't know where
> we can put the downloaded images such as
> "home"/.cache/coreapp/images/
>
> Conclusion: homepath is needed
>
>
>
> Feel free to prove I am wrong :P because I am
> confusing about the offline mode of the RSS
> reader Core App
>
> Have a nice day :)
>
>
>
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