My "drawView" function is being called only once? - iphone

Question

I'm new to OpenGL ES and having a simple kind of problem in my project. I've successfully drawn a square on my screen but the problem is that my "drawView" function in my EAGLView is
only called once however I wrote code to call it again n again as in Xcode's OpenGL ES Template.
Do anyone have clue where's the mistake?
Following is the code of my EAGLView.m file:
#import <QuartzCore/QuartzCore.h>
#import <OpenGLES/EAGLDrawable.h>
#import "EAGLView.h"
#define USE_DEPTH_BUFFER 0
// A class extension to declare private methods
#interface EAGLView ()
#property (nonatomic, retain) EAGLContext *context;
- (BOOL) createFramebuffer;
- (void) destroyFramebuffer;
#end
#implementation EAGLView
#synthesize context;
#synthesize animating;
#dynamic animationFrameInterval;
// You must implement this method
+ (Class)layerClass {
return [CAEAGLLayer class];
}
//The GL view is stored in the nib file. When it's unarchived it's sent -initWithCoder:
- (id)initWithCoder:(NSCoder*)coder {
if ((self = [super initWithCoder:coder])) {
// Get the layer
CAEAGLLayer *eaglLayer = (CAEAGLLayer *)self.layer;
eaglLayer.opaque = YES;
eaglLayer.drawableProperties = [NSDictionary dictionaryWithObjectsAndKeys:
[NSNumber numberWithBool:NO], kEAGLDrawablePropertyRetainedBacking, kEAGLColorFormatRGBA8, kEAGLDrawablePropertyColorFormat, nil];
context = [[EAGLContext alloc] initWithAPI:kEAGLRenderingAPIOpenGLES1];
if (!context || ![EAGLContext setCurrentContext:context]) {
[self release];
return nil;
}
animating = FALSE;
displayLinkSupported = FALSE;
animationFrameInterval = 1;
displayLink = nil;
animationTimer = nil;
// A system version of 3.1 or greater is required to use CADisplayLink. The NSTimer
// class is used as fallback when it isn't available.
NSString *reqSysVer = #"3.1";
NSString *currSysVer = [[UIDevice currentDevice] systemVersion];
if ([currSysVer compare:reqSysVer options:NSNumericSearch] != NSOrderedAscending)
displayLinkSupported = TRUE;
}
return self;
}
- (void)drawView {
NSLog(#"In EAGLView's drawView func");
static const GLfloat squareVertices[] = {
-0.5f, -0.33f,
0.5f, -0.33f,
-0.5f, 0.33f,
0.5f, 0.33f,
};
static const GLubyte squareColors[] = {
255, 0, 0, 255,
0, 255, 0, 255,
0, 0, 255, 255,
0, 0, 0, 0,
};
[EAGLContext setCurrentContext:context];
glBindFramebufferOES(GL_FRAMEBUFFER_OES, viewFramebuffer);
glViewport(0, 0, backingWidth, backingHeight);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
glRotatef(10.0f, 0.0f, 0.0f, 1.0f);
glClearColor(0.5f, 0.5f, 0.5f, 1.0f);
glClear(GL_COLOR_BUFFER_BIT);
glVertexPointer(2, GL_FLOAT, 0, squareVertices);
glEnableClientState(GL_VERTEX_ARRAY);
glColorPointer(4, GL_UNSIGNED_BYTE, 0, squareColors);
glEnableClientState(GL_COLOR_ARRAY);
glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
glBindRenderbufferOES(GL_RENDERBUFFER_OES, viewRenderbuffer);
[context presentRenderbuffer:GL_RENDERBUFFER_OES];
}
- (void)layoutSubviews {
[EAGLContext setCurrentContext:context];
[self destroyFramebuffer];
[self createFramebuffer];
[self drawView];
}
- (BOOL)createFramebuffer {
glGenFramebuffersOES(1, &viewFramebuffer);
glGenRenderbuffersOES(1, &viewRenderbuffer);
glBindFramebufferOES(GL_FRAMEBUFFER_OES, viewFramebuffer);
glBindRenderbufferOES(GL_RENDERBUFFER_OES, viewRenderbuffer);
[context renderbufferStorage:GL_RENDERBUFFER_OES fromDrawable:(CAEAGLLayer*)self.layer];
glFramebufferRenderbufferOES(GL_FRAMEBUFFER_OES, GL_COLOR_ATTACHMENT0_OES, GL_RENDERBUFFER_OES, viewRenderbuffer);
glGetRenderbufferParameterivOES(GL_RENDERBUFFER_OES, GL_RENDERBUFFER_WIDTH_OES, &backingWidth);
glGetRenderbufferParameterivOES(GL_RENDERBUFFER_OES, GL_RENDERBUFFER_HEIGHT_OES, &backingHeight);
if (USE_DEPTH_BUFFER) {
glGenRenderbuffersOES(1, &depthRenderbuffer);
glBindRenderbufferOES(GL_RENDERBUFFER_OES, depthRenderbuffer);
glRenderbufferStorageOES(GL_RENDERBUFFER_OES, GL_DEPTH_COMPONENT16_OES, backingWidth, backingHeight);
glFramebufferRenderbufferOES(GL_FRAMEBUFFER_OES, GL_DEPTH_ATTACHMENT_OES, GL_RENDERBUFFER_OES, depthRenderbuffer);
}
if(glCheckFramebufferStatusOES(GL_FRAMEBUFFER_OES) != GL_FRAMEBUFFER_COMPLETE_OES) {
NSLog(#"failed to make complete framebuffer object %x", glCheckFramebufferStatusOES(GL_FRAMEBUFFER_OES));
return NO;
}
return YES;
}
- (void)destroyFramebuffer {
glDeleteFramebuffersOES(1, &viewFramebuffer);
viewFramebuffer = 0;
glDeleteRenderbuffersOES(1, &viewRenderbuffer);
viewRenderbuffer = 0;
if(depthRenderbuffer) {
glDeleteRenderbuffersOES(1, &depthRenderbuffer);
depthRenderbuffer = 0;
}
}
- (NSInteger)animationFrameInterval
{
return animationFrameInterval;
}
- (void)setAnimationFrameInterval:(NSInteger)frameInterval
{
// Frame interval defines how many display frames must pass between each time the
// display link fires. The display link will only fire 30 times a second when the
// frame internal is two on a display that refreshes 60 times a second. The default
// frame interval setting of one will fire 60 times a second when the display refreshes
// at 60 times a second. A frame interval setting of less than one results in undefined
// behavior.
if (frameInterval >= 1)
{
animationFrameInterval = frameInterval;
if (animating)
{
[self stopAnimation];
[self startAnimation];
}
}
}
- (void)startAnimation
{
if (!animating)
{
if (displayLinkSupported)
{
// CADisplayLink is API new to iPhone SDK 3.1. Compiling against earlier versions will result in a warning, but can be dismissed
// if the system version runtime check for CADisplayLink exists in -initWithCoder:. The runtime check ensures this code will
// not be called in system versions earlier than 3.1.
displayLink = [NSClassFromString(#"CADisplayLink") displayLinkWithTarget:self selector:#selector(drawView)];
[displayLink setFrameInterval:animationFrameInterval];
[displayLink addToRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];
}
else
animationTimer = [NSTimer scheduledTimerWithTimeInterval:(NSTimeInterval)((1.0 / 60.0) * animationFrameInterval) target:self selector:#selector(drawView) userInfo:nil repeats:TRUE];
animating = TRUE;
}
}
- (void)stopAnimation
{
if (animating)
{
if (displayLinkSupported)
{
[displayLink invalidate];
displayLink = nil;
}
else
{
[animationTimer invalidate];
animationTimer = nil;
}
animating = FALSE;
}
}
- (void)dealloc {
if ([EAGLContext currentContext] == context) {
[EAGLContext setCurrentContext:nil];
}
[context release];
[super dealloc];
}
#end

Answer 1

Check to see if your method:
- (void)startAnimation
is actually being called.