file read and write

There is a virtual file system in MoSync. It can't access existing files on the devices, but you can read and write your own files through the storage system. You need to inlcude MAFS.lib into your project, and then you can use standard C filestream commands (fopen, fwrite, etc). There aren't any MoSync specific tutorials at the moment on these, but the documentation here http://www.cplusplus.com/reference/clibrary/cstdio/ will be very useful.

Let me know if you've got any specific questions about this.

Thanks

Ok, I've done this a lot. What you don't want to use is the virtual file system. What you want are MoSync stores.

What you would do is to save the PNG data to a store. When you open the store, you read the data into a placeholder, and then use maCreateImageFromData(). This will rebuild the image resource.

Have a look at the tutorial 'Reading and Writing Data'.

I've also written an ImageCache class. You request URLs of images from it. If it hasn't got it, it downloads it and stores in as a store. If it has already got it, it just loads it from the store and returns it to you. Its on another machine at the moment, but if I get a chance later, I'll post the code.

Sorry this is so brief

[attachment=0]ImageCacheListener.h[/attachment]
[attachment=1]ImageCache.h[/attachment]
[attachment=2]ImageCache.cpp[/attachment]

Have a look at this code. It downloads and saves PNG images to the device, using an MD5 hash of their original URL as a filename. You can see how to save and load images using it.

Hope this helps.

These files are for educational purposes only, showing how to store images and load them again from storage. It was part of a much larger application

That's just debug. My ImageCache calls out to my web server, which returns resized images (there's no point sending massive, desktop sized pictures to the phone). It's just so I can see the url it is requesting from

Yes, each image is stored in its own file. I've not done any performance analysis, but it will definitely be faster having images in their own file, and not concatenated together.

Yes, the Mapping is between md5 fingerprints and any MAHandle already loaded.

You can't poke values into stores. You have to read the entire store into a data object, change the value, and then write the entire store back.

Hope this helps.

I'll send you my md5 code (and b64 code) if you really want it. I'll post ImageCacheRequest.cpp tomorrow if you want it, but I can't promise it will fix all of your problems as it probably has links into other things as well.

Hi,

I'v got a problem on writing downloaded image to store. I got "Invalid resource type" error without any more information. The following is the complete code.
Could you please have a look at it? Thanks a lot!
Writting store code snip is in function: void finishedDownloading(Downloader *dl, MAHandle data)
#include
#include
#include
#include
#include
#include
using namespace MAUtil;
using namespace MAUI;
class MyScreen: public Screen, DownloadListener {
public:
MyScreen() {
lprintfln("Starting application");
idl = new ImageDownloader();
idl->addDownloadListener(this);
imageResource = maCreatePlaceholder();
lprintfln("Starting download");
String url =
"http://shop.abc.net.au/multimediaitems/images/product_images/4/482912.png";
idl->beginDownloading(url.c_str(), imageResource);
}
~MyScreen() {
delete idl;
maDestroyObject(imageResource);
}
//DownloadListener methods
void downloadCancelled(Downloader *dl) {
lprintfln("Cancelled");
}
void error(Downloader *dl, int code) {
lprintfln("Error: %d", code);
}
void finishedDownloading(Downloader *dl, MAHandle data) {
lprintfln("Completed download");
//Create a new image on screen with this picture
Image* i = new Image(0, 0, 240, 320, NULL, false, false, imageResource);
MAHandle store = maOpenStore("hello", MAS_CREATE_IF_NECESSARY);
maWriteStore(store, data);
maCloseStore(store, 0);
this->setMain(i);
this->show();
}
void notifyProgress(Downloader *dl, int downloadedBytes, int totalBytes) {
lprintfln("Downloaded %d of %d bytes", downloadedBytes, totalBytes);
}
private:
ImageDownloader* idl;
MAHandle imageResource;
};
class MAUIMoblet: public Moblet {
public:
MAUIMoblet() {
// initialize
screen = new MyScreen();
}
void keyPressEvent(int keyCode) {
// todo: handle key presses
}
void keyReleaseEvent(int keyCode) {
// todo: handle key releases
}
MyScreen* screen;
~MAUIMoblet() {
delete screen;
}
};
extern "C" int MAMain() {
Moblet::run(new MAUIMoblet());
return 0;
};

I tried Downloader, not working. And maCreateImageFromData is another topic about creating image.
Not working in phone either, but could you try it on your phone, maybe I do it incorrectly. But I believe, the emulator should support this.
Thanks.

OK, It seems that you can't write an Image resource to storage in the way I thought. If you are downloading and storing images, then you need to do a normal download, and call maCreateImageFromRaw().

I've tested this code.

#include
#include
#include
#include
#include
#include

using namespace MAUtil;
using namespace MAUI;
class MyScreen: public Screen, DownloadListener {
public:
MyScreen() {
lprintfln("Starting application");
idl = new Downloader();
idl->addDownloadListener(this);
imageResource = maCreatePlaceholder();
lprintfln("Starting download");
String url =
"http://shop.abc.net.au/multimediaitems/images/product_images/4/482912.png";
idl->beginDownloading(url.c_str());
}
~MyScreen() {
delete idl;
maDestroyObject(imageResource);
}
//DownloadListener methods
void downloadCancelled(Downloader *dl) {
lprintfln("Cancelled");
}
void error(Downloader *dl, int code) {
lprintfln("Error: %d", code);
}

void finishedDownloading(Downloader *dl, MAHandle data)
{
lprintfln("Completed download");
//Create a new image on screen with this picture
maCreateImageFromData(imageResource, data, 0, maGetDataSize(data));
Image* i = new Image(0, 0, 240, 320, NULL, false, false, imageResource);
MAHandle store = maOpenStore("hello", MAS_CREATE_IF_NECESSARY);
maWriteStore(store, data);
maCloseStore(store, 0);
this->setMain(i);
this->show();
}

void notifyProgress(Downloader *dl, int downloadedBytes, int totalBytes) {
lprintfln("Downloaded %d of %d bytes", downloadedBytes, totalBytes);
}
private:
Downloader* idl;
MAHandle imageResource;
};

class MAUIMoblet : public Moblet {
public:
MAUIMoblet() {
// initialize
screen = new MyScreen();
screen->show();
}

void keyPressEvent(int keyCode) {
// todo: handle key presses
}

void keyReleaseEvent(int keyCode) {
// todo: handle key releases
}
MyScreen* screen;

~MAUIMoblet() {
delete screen;
}

};

extern "C" int MAMain() {
Moblet::run(new MAUIMoblet());
return 0;
};

Wholly unofficially

http://www.screencast.com/t/Mzk2MDM0ZG

MAHandle store = maOpenStore("hello", 0);
if(store != STERR_NONEXISTENT) {
maWriteStore(store, data);
maCloseStore(store, 
}

That code is not safe. Store access may fail for any reason, so it should look more like this:

MAHandle store = maOpenStore("hello", MAS_CREATE_IF_NECESSARY);
if(store <  {
  // Show error message.
} else {
  maWriteStore(store, data);
  maCloseStore(store, 
}

maWriteStore() completely overwrites the existing store, so if you keep writing to a store with the same name, the memory will not become full.

MAHandle store = maOpenStore("hello", 0);
if(store != STERR_NONEXISTENT) {
maWriteStore(store, data);
maCloseStore(store,
}

I don't think that this will work - have you tried it?

If the store DOES already exist (i.e. it is not non-existent), then it will save, but we've already got got it. If it DOESN'T exist, it isn't created because there is no MAS_CREATE_IF_NECESSARY, and it isn't saved. You can't create new stores.

If you change store != STERR_NONEXISTENT to store == STERR_NONEXISTENT then if it DOES exist it won't be saved, and if it DOESN'T exist it can't be created. I think you need

MAHandle store = maOpenStore("hello", 0);
if(store == STERR_NONEXISTENT) 
{
store = maOpenStore("hello", MAS_CREATE_IF_NECESSARY);
maWriteStore(store, data);
maCloseStore(store, 0);
} 

When you save a store which is already on the device, then the old store is overwritten, so you won't just fill up the device. You can't append to a store currently, but I think that there is some work to add this functionality.

Hi Sam,
Actually I already try ImageCacheStarterApp. In ImageCache.cpp you save the image to store like this

void ImageCache::finishedDownloading(Downloader* downloader, MAHandle data){	
//Save to storage	
MAHandle store = maOpenStore(mMD5url.c_str(), MAS_CREATE_IF_NECESSARY);	
maWriteStore(store, data);	
maCloseStore(store, 0);	
returnImage(data);
}

And then I try another example from you. It is ImageDownloader. I add the same code to ImageDownloader

void ImageCache::finishedDownloading(Downloader* downloader, MAHandle data){	
//Save to storage        
String storeName = "img1";	
MAHandle store = maOpenStore(storeName.c_str(), MAS_CREATE_IF_NECESSARY);	
maWriteStore(store, data);	
maCloseStore(store, 0);
}

I think, nothing wrong with the code, but I got this error when I run it :

[14] Emulator connected.
[14] Starting download
[14] Downloaded 0 bytes
[14] Downloaded 4356 bytes
[14] Downloaded 5808 bytes
[14] Downloaded 8712 bytes
[14] Downloaded 11616 bytes
[14] Downloaded 13018 bytes
[14] Finished downloading
[14] MoSync Panic 40001. "Invalid resource type" The panic occurred in the syscall maWriteStore.

can you tell me why? because I think they are using the same code to save to the store.
Thanks a lot.

Hmm it is a bit odd. It may be because that ImageCache downloads a standard binary resource. In ImageDownloader, it call maCreateImageFromData to create an image resource. It may be that you can't save the image resource. You will may have to save it before maCreateImageFromData() is called,