OpenGLES2之Android&iOS跨平台开发教程（二）i

前言

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上一篇介绍了在Android端构建OpenGLES，这一篇介绍在iOS端调用OpenGLES。

步骤

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1.创建Xcode工程，链接GLKit.framework

framework

2.将上一篇中创建的GLES文件夹添加到工程

GLES

可以看到，大部分代码都可以在Common下用C++实现，Android、iOS用来写平台相关的代码，并封装调用C++的接口。

3.创建GLESViewController继承GLKViewController

GLESViewController.h ↓

#import <GLKit/GLKit.h>
#import "Renderer.h"

@interface GLESViewController : GLKViewController

- (id)initWithView:(UIView*)view;

@end

GLESViewController.mm ↓ 因为包含了C++代码，所以文件名后缀应为mm

#import "GLESViewController.h"

@interface GLESViewController ()

@property (strong, nonatomic) EAGLContext *context;

@end

@implementation GLESViewController

- (id)initWithView:(UIView*)view
{
    if (self = [super init]) {
        
        self.context = [[EAGLContext alloc] initWithAPI:kEAGLRenderingAPIOpenGLES2];
        
        if (!self.context) {
            NSLog(@"Failed to create ES context");
        }
        
        GLKView *glkView = [[GLKView alloc] initWithFrame:[view bounds] context:self.context];
        glkView.drawableDepthFormat = GLKViewDrawableDepthFormat24;
        glkView.userInteractionEnabled = YES;   //启用视图交互
        glkView.multipleTouchEnabled = YES;     //启用多点触摸
        glkView.autoresizingMask = UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight;
        
        self.view = glkView;
        self.preferredFramesPerSecond = 60;
        
        float scale = [[UIScreen mainScreen] scale];
        //NSLog(@"scale: %f", scale);
        [EAGLContext setCurrentContext:self.context];
        surfaceCreated();
        surfaceChanged([view bounds].size.width * scale, [view bounds].size.height * scale);
        
        [view addSubview:self.view];
    }
    return self;
}

- (void)viewWillLayoutSubviews {
    //NSLog(@"view bounds: %@", NSStringFromCGRect([self.view bounds]));
    float scale = [[UIScreen mainScreen] scale];
    surfaceChanged([self.view bounds].size.width * scale, [self.view bounds].size.height * scale);
}

- (void)dealloc
{
    if ([EAGLContext currentContext] == self.context) {
        [EAGLContext setCurrentContext:nil];
    }
}

#pragma mark - GLKView and GLKViewController delegate methods

- (void)glkView:(GLKView *)view drawInRect:(CGRect)rect
{
    drawFrame();
}

@end

这里的initWithView相当于Android GLSurfaceView的onSurfaceCreated，
viewWillLayoutSubviews相当于onSurfaceChanged，
drawInRect相当于onDrawFrame，还是很容易理解的。

4.显示GLES视图

这里我还是按Android端的习惯，把GLESView添加为一个UIView的子视图，这个在initWithView函数中完成了，还要把GLESViewController添加为当前ViewController的子视图控制器，否则drawInRect只会在初始化时调用一次，不会每帧调用。
ViewController.m ↓

#import "ViewController.h"
#import "GLESViewController.h"

@interface ViewController ()

@property (weak, nonatomic) IBOutlet UIView *showView;
@property (strong, nonatomic) GLESViewController *glesViewController;

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    
    // 创建GLES视图并添加
    self.glesViewController = [[GLESViewController alloc] initWithView:self.showView];
    [self addChildViewController:self.glesViewController];
}


- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

@end

iOS运行结果

后记

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• Demo工程下载