A fast, easy to use, free, and community supported 2D game engine
mistergoomba
Member
Does anyone know of any good sample source out there for preloading assets? I can only assume I haven't found anything because it's such a basic thing that anyone should be able to do it, but I'm just clueless right now. The only thing I've been able to do is use "applicationDidFinishLaunching" to notify me that the assets have been cached and cocos2d's texture/sound manager to load in the resources.
Any tutorials or sample projects that you know of would be very helpful. Thanks!
It depends what your wanting to pre load.
If its images you could use the new (in 0.8) async loading code:
[[TextureMgr sharedTextureMgr] addImageAsync:@"image.png" target:self selector:@selector(imageLoaded:)];
And the custom imageLoaded: selector will be called once its complete. Theres demos of it in the main coco2d download, with some notes to bare in mind (images may complete loading in a different order than they were added etc).
For audio, the CocosDenshion lib has an async loading method, again examples in the main download.
I believe anything you load in the init method directly, using regular (non-async) code will be loaded before that object loads/shows on screen. So the initial scene/layers you load on your games launch should have their assets loaded by the time they run (I may be wrong, but think thats the case).
Here's some stuff for you. The code is untested and probably has syntax errors since I haven't typed it into xcode, but you should get a good idea of what's needed ;-)
Create a CocosNode subclass that contains your progress bar, along with a property that allows you to set the progress:
@property(readwrite,assign) int percentComplete;
In your setter, move your progress bar:
// Leftmost and rightmost position of the loading bar sprite in pixels #define kLoadingBarPosition0 25.0f #define kLoadingBarPosition100 238.0f #define kLoadingBarSpread (kLoadingBarPosition100 - kLoadingBarPosition0) - (void) setPercentComplete { percentComplete = value; float xPosition = (kLoadingBarSpread * value) / 100.0f; loadingBar.position = ccp(xPosition + kLoadingBarPosition0, loadingBar.position.y); loadingComplete.visible = value >= 100; }
Somewhere in your code, make a list of resources you want to load:
NSArray* imagesToPreload; ... imagesToPreload = [self getImagesWeWantToPreload];
There are two ways to load things asynchronously. The easier way is to use the async convenience methods available in cocos:
int nextImageIndex = 0;
- (void) imageLoaded:(Texture2D*) tex
{
myLoadingBar.percentComplete = (nextImageIndex * 100) / [imagesToPreload count];
if(nextImageIndex >= [imagesToPreload count])
{
// All images loaded. Do something like let the user tap to continue.
return;
}
NSString* nextFilename = [imagesToPreload objectAtIndex:lastImageIndex];
nextImageIndex++;
[[TextureMgr sharedTextureMgr] addImageAsync:nextFilename target:self selector:@selector(imageLoaded:)];
}
Now just call [self imageLoaded:nil] to start it going.
Another method is to put the whole thing into a separate thread using NSOperation. The code below is a bit more generic because I used this pattern to load all sorts of things asynchronously and send an update containing the proportion of resources that have been loaded.
Note that you MUST create your own autorelease pool since this is a different thread, and you must set the GL context. As well, you must call selectors using the main thread.
@interface PreloadOperation : NSOperation
{
NSArray* imagesToPreload;
id target;
SEL selector;
}
// init methods omitted
@end
@implementation PreloadOperation
- (void)main
{
NSAutoreleasePool *autoreleasepool = [[NSAutoreleasePool alloc] init];
EAGLContext* oldContext = [EAGLContext currentContext];
EAGLContext* context = [[EAGLContext alloc]
initWithAPI:kEAGLRenderingAPIOpenGLES1
sharegroup:[[[[Director sharedDirector] openGLView] context] sharegroup]];
if(nil == context)
{
NSLog(@"ResourcePreloader: could not create EAGL context");
goto done;
}
if(![EAGLContext setCurrentContext:context])
{
NSLog(@"ResourcePreloader: could not set EAGL context");
goto done;
}
int totalResources = [imagesToPreload count];
int loadedResources = 0;
float lastCompleteAmount = 0;
for(NSString* filename in imageFilenames)
{
if([self isCancelled])
{
goto done;
}
[[TextureMgr sharedTextureMgr] addImage:filename];
loadedResources++;
float complete = ((float)loadedResources) / totalResources;
if(1.0 == complete)
{
complete = 0.99999999;
}
if(complete >= lastCompleteAmount + kCompletionUpdateThreshold)
{
lastCompleteAmount = complete;
[target performSelectorOnMainThread:selector withObject:[NSNumber numberWithFloat:lastCompleteAmount] waitUntilDone:NO];
}
}
done:
[[ResourcePreloader sharedInstance] notifyAsyncOperationComplete];
[EAGLContext setCurrentContext:oldContext];
[context release];
if(![self isCancelled])
{
[target performSelectorOnMainThread:selector withObject:[NSNumber numberWithFloat:1.0] waitUntilDone:YES];
}
[autoreleasepool release];
}
@end
To start it going, make an operation queue and add the operation. You can make the queue in a global context and make use of it as needed. You can also call cancel on the operation if you need to stop it.
NSOperationQueue * queue = [[NSOperationQueue alloc] init]; preloadOperation = [PreloadOperation operationWithTarget:target selector:selector animations:animationResources sounds:soundResources images:imageResources]; [queue addOperation:preloadOperation];
Here is some rather generic code I wrote:
//
// LoadingScene.m
// Astralis
//
// Created by Brian Dittmer on 1/8/10.
// Copyright 2010 Sad Robot Software. All rights reserved.
//
#import "LoadingScene.h"
#import "StarGunnerConstants.h"
@implementation LoadingScene
@synthesize textures;
- (id) init {
if((self = [super init]) == nil) return nil;
CCSprite *bg = [CCSprite spriteWithFile:@"Default.png"];
bg.position = ccp(160, 240);
[self addChild:bg z:0];
CCSprite *loadingStatusBackground = [CCSprite spriteWithFile:@"loading_progress_background.png"];
loadingStatusBackground.anchorPoint = ccp(0,0);
loadingStatusBackground.position = ccp(22, 150);
[self addChild:loadingStatusBackground z:1];
CCSprite *loadingStatusForeground = [CCSprite spriteWithFile:@"loading_progress_foreground.png"];
loadingStatusForeground.anchorPoint = loadingStatusBackground.anchorPoint;
loadingStatusForeground.position = loadingStatusBackground.position;
loadingStatusForeground.scaleX = 0;
[self addChild:loadingStatusForeground z:2 tag:1];
CCBitmapFontAtlas *loadingText = [CCBitmapFontAtlas bitmapFontAtlasWithString:@" " fntFile:@"visitor_12pt_green.fnt"];
loadingText.anchorPoint = loadingStatusBackground.anchorPoint;
loadingText.position = ccp(loadingStatusBackground.position.x, loadingStatusBackground.position.y - 15);
[self addChild:loadingText z:2 tag:2];
return self;
}
- (void) onEnter {
[super onEnter];
NSError *error;
NSArray *bundleContents = [[NSFileManager defaultManager] contentsOfDirectoryAtPath:[[NSBundle mainBundle] bundlePath] error:&error];
self.textures = [NSMutableArray arrayWithCapacity:[bundleContents count]];
for(NSString *file in bundleContents) {
if([[file pathExtension] compare:@"png"] == NSOrderedSame) {
[textures addObject:[file lastPathComponent]];
}
}
numberOfLoadedTextures = 0;
[(CCBitmapFontAtlas*)[self getChildByTag:2] setString:[NSString stringWithFormat:@"Loading %@...", [textures objectAtIndex:numberOfLoadedTextures]]];
[[CCTextureCache sharedTextureCache] addImageAsync:[textures objectAtIndex:numberOfLoadedTextures] target:self selector:@selector(imageDidLoad:)];
}
- (void) imageDidLoad:(CCTexture2D*)tex {
NSString *plistFile =
[[(NSString*)[textures objectAtIndex:numberOfLoadedTextures] stringByDeletingPathExtension] stringByAppendingString:@".plist"];
if([[NSFileManager defaultManager] fileExistsAtPath:[[[NSBundle mainBundle] bundlePath] stringByAppendingPathComponent:plistFile]]) {
[[CCSpriteFrameCache sharedSpriteFrameCache] addSpriteFramesWithFile:plistFile];
NSLog(@"loading %@", plistFile);
}
numberOfLoadedTextures++;
CCSprite *loadingStatusForeground = (CCSprite*)[self getChildByTag:1];
loadingStatusForeground.scaleX = (float)numberOfLoadedTextures / (float)[textures count];
if(numberOfLoadedTextures == [textures count]) {
[[NSNotificationCenter defaultCenter] postNotificationName:kPreloadingDone object:nil];
} else {
[(CCBitmapFontAtlas*)[self getChildByTag:2] setString:[NSString stringWithFormat:@"Loading %@...", [textures objectAtIndex:numberOfLoadedTextures]]];
[[CCTextureCache sharedTextureCache] addImageAsync:[textures objectAtIndex:numberOfLoadedTextures] target:self selector:@selector(imageDidLoad:)];
}
}
- (void) dealloc {
[textures release];
}
@endBasically it searches the app bundle for pngs (this can be expanded upon, we only use pngs though) and then loads them one at a time into the texture cache. It also looks for plist files with the same name as the png (albeit it with a different extension) and loads those into the spriteframe cache.
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