cocos2D-x游戏开发多线程

Cocos2d-x 2019-05-18

原创文章，转载请注明出处：http://www.jb51.cc/article/p-raudppry-o.html

cocos2d-x引擎在内部实现了一个庞大的主循环，每帧之间更新界面，如果耗时的操作放到了主线程中，游戏的界面就会卡，这是不能容忍的，游戏最基本的条件就是流畅性，这就是为什么游戏开发选择C++的原因。另外现在双核手机和四核手机越来越普遍了，是时候使用多线程来挖掘硬件的潜力了。

1.环境搭建

cocos2d-x中的多线程使用pthread就可以实现跨平台，而且也不是很难理解。使用pthread需要先配置一下工程。右击工程----->属性----->配置属性---->链接器----->输入---->附加依赖项中添加pthreadVCE2.lib，如下图


接着添加附加包含目录，右击项目，属性----->C/C++---->常规----->附加包含目录加入pthread头文件所在的目录


这样，环境就搭建起来了。

2.多线程的使用

使用pthread来实现多线程，最重要的一个函数是

[cpp] view plain copy print ?
  1. PTW32_DLLPORT int PTW32_CDECL pthread_create (pthread_t * tid,//线程的标示
  2. const pthread_attr_t * attr,//创建线程的参数
  3. void *(*start) (void *),//入口函数的指针
  4. void *arg); //传递给线程的数据

在HelloWorldScene.h文件中

[cpp] view plain copy print ?
  1. pthread_t pidrun,pidgo;
  2. static void* th_run(void *r);
  3. static void* th_go(void *r);
定义了两个函数和两个线程的标识。

然后自定义了一个类，用于给线程传递数据。Student类如下：

[cpp] view plain copy print ?
  1. #pragma once
  2. #include <string>
  3. class Student
  4. {
  5. public:
  6. Student(void);
  7. Student(std::string name,int age,std::string sex);
  8. ~Student(void);
  10. std::string name;
  11. int age;
  12. std::string sex;
  14. };

源文件如下

[cpp] view plain copy print ?
  1. #include "Student.h"
  2. #include "cocos2d.h"
  4. Student::Student(void)
  5. {
  6. }
  9. Student::~Student(void)
  10. {
  11. cocos2d::cclog("delete data");
  12. }
  13. Student::Student(std::string name,std::string sex)
  14. {
  15. this->name=name;
  16. this->age=age;
  17. this->sex=sex;
  18. }
在退出菜单的回调函数中启动两个线程：

[cpp] view plain copy print ?
  1. void HelloWorld::menuCloseCallback(CCObject* pSender)
  2. {
  4. Student *temp=new Student(std::string("zhycheng"),23,std::string("male"));
  5. pthread_mutex_init(&mutex,NULL);
  6. pthread_create(&pidrun,NULL,th_run,temp);//启动线程
  7. pthread_create(&pidgo,th_go,0);
  9. }

可以看到，将Student的指针传递给了pidrun线程，那么在pidrun线程中获得Student信息如下：

[cpp] view plain copy print ?
  1. Student *s=(Student*)(r);
  2. cclog("name is %s,and age is %d,sex is %s",s->name.c_str(),s->age,s->sex.c_str());
  3. delete s;

3.线程同步

使用了线程，必然就要考虑到线程同步，不同的线程同时访问资源的话，访问的顺序是不可预知的，会造成不可预知的结果。

这里使用pthread_mutex_t来实现同步，下面我来演示一下使用多线程实现卖票系统。卖票的时候，是由多个窗口同时卖票，这里要做到一张票不要卖出去两次，不要出现有票却无法卖的结果。

在线程函数th_run和th_go中来卖票，票的数量是一个全局变量，每卖出去一张票，就将票的数量减一。其中同步的pthread_mutex_t也是一个全局变量，就用它来实现线程同步。

[cpp] view plain copy print ?
  1. void* HelloWorld::th_run(void *r)
  2. {
  4. Student *s=(Student*)(r);
  5. cclog("name is %s,s->sex.c_str());
  6. delete s;
  7. while(true)
  8. {
  9. pthread_mutex_lock(&mutex);
  10. if(ticket>0)
  11. {
  12. cclog("thread run sell %d",ticket);
  13. ticket--;
  14. pthread_mutex_unlock(&mutex);
  15. }
  16. else
  17. {
  18. pthread_mutex_unlock(&mutex);
  19. break;
  20. }
  22. Sleep(1);
  23. //Usleep(10);
  24. }
  26. return NULL;
  27. }

[cpp] view plain copy print ?
  1. void* HelloWorld::th_go(void *r)
  2. {
  4. while(true)
  5. {
  6. pthread_mutex_lock(&mutex);
  7. if(ticket>0)
  8. {
  9. cclog("thread go sell %d",ticket);
  10. ticket--;
  11. pthread_mutex_unlock(&mutex);
  12. }
  13. else
  14. {
  15. pthread_mutex_unlock(&mutex);
  16. break;
  18. }
  20. Sleep(1);
  22. }
  23. return NULL;
  24. }


mutex被锁定后，其他线程若再想锁定mutex的话，必须等待，当该线程释放了mutex之后，其他线程才能锁定mutex。Sleep()函数可以使得该线程休眠，单位是毫秒。下面是卖票的结果：

[cpp] view plain copy print ?
  1. name is zhycheng,and age is 23,sex is male
  2. delete data
  3. thread run sell 100
  4. thread run sell 99
  5. thread go sell 98
  6. thread go sell 97
  7. thread run sell 96
  8. thread go sell 95
  9. thread go sell 94
  10. thread run sell 93
  11. thread go sell 92
  12. thread run sell 91
  13. thread go sell 90
  14. thread go sell 89
  15. thread run sell 88
  16. thread go sell 87
  17. thread run sell 86
  18. thread go sell 85
  19. thread run sell 84
  20. thread go sell 83
  21. thread run sell 82
  22. thread go sell 81
  23. thread run sell 80
  24. thread go sell 79
  25. thread run sell 78
  26. thread go sell 77
  27. thread run sell 76
  28. thread go sell 75
  29. thread run sell 74
  30. thread go sell 73
  31. thread run sell 72
  32. thread go sell 71
  33. thread run sell 70
  34. thread go sell 69
  35. thread go sell 68
  36. thread run sell 67
  37. thread go sell 66
  38. thread run sell 65
  39. thread go sell 64
  40. thread run sell 63
  41. thread go sell 62
  42. thread run sell 61
  43. thread go sell 60
  44. thread run sell 59
  45. thread go sell 58
  46. thread run sell 57
  47. thread go sell 56
  48. thread run sell 55
  49. thread go sell 54
  50. thread run sell 53
  51. thread run sell 52
  52. thread go sell 51
  53. thread run sell 50
  54. thread go sell 49
  55. thread run sell 48
  56. thread go sell 47
  57. thread run sell 46
  58. thread go sell 45
  59. thread run sell 44
  60. thread run sell 43
  61. thread go sell 42
  62. thread run sell 41
  63. thread run sell 40
  64. thread go sell 39
  65. thread run sell 38
  66. thread run sell 37
  67. thread run sell 36
  68. thread run sell 35
  69. thread go sell 34
  70. thread run sell 33
  71. thread run sell 32
  72. thread go sell 31
  73. thread run sell 30
  74. thread run sell 29
  75. thread run sell 28
  76. thread run sell 27
  77. thread run sell 26
  78. thread run sell 25
  79. thread go sell 24
  80. thread run sell 23
  81. thread go sell 22
  82. thread go sell 21
  83. thread run sell 20
  84. thread go sell 19
  85. thread run sell 18
  86. thread run sell 17
  87. thread go sell 16
  88. thread run sell 15
  89. thread go sell 14
  90. thread go sell 13
  91. thread run sell 12
  92. thread go sell 11
  93. thread go sell 10
  94. thread run sell 9
  95. thread go sell 8
  96. thread run sell 7
  97. thread go sell 6
  98. thread go sell 5
  99. thread run sell 4
  100. thread go sell 3
  101. thread run sell 2
  102. thread run sell 1


可以看到，这个打印结果正确无误。如果不加mutex会是什么样的结果呢，我将线程同步的mutex注释掉，输出的结果为：

[cpp] view plain copy print ?
  1. name is zhycheng,sex is male
  2. delete data
  3. thread run sell 100
  4. thread run sell 99
  5. thread run sell 98
  6. thread go sell 97
  7. thread run sell 96
  8. thread go sell 95
  9. thread run sell 94
  10. thread go sell 94
  11. thread run sell 92
  12. thread run sell 91
  13. thread go sell 90
  14. thread run sell 89
  15. thread go sell 88
  16. thread run sell 87
  17. thread run sell 86
  18. thread go sell 86
  19. thread go sell 84
  20. thread run sell 83
  21. thread go sell 82
  22. thread run sell 81
  23. thread go sell 80
  24. thread run sell 79
  25. thread run sell 78
  26. thread go sell 77
  27. thread run sell 76
  28. thread run sell 75
  29. thread go sell 74
  30. thread run sell 73
  31. thread go sell 72
  32. thread run sell 71
  33. thread go sell 70
  34. thread go sell 69
  35. thread run sell 68
  36. thread go sell 67
  37. thread go sell 66
  38. thread run sell 65
  39. thread go sell 64
  40. thread go sell 63
  41. thread run sell 62
  42. thread go sell 61
  43. thread run sell 60
  44. thread run sell 59
  45. thread run sell 58
  46. thread run sell 57
  47. thread run sell 56
  48. thread run sell 55
  49. thread go sell 54
  50. thread run sell 54
  51. thread go sell 52
  52. thread run sell 52
  53. thread go sell 50
  54. thread run sell 50
  55. thread go sell 49
  56. thread run sell 47
  57. thread go sell 47
  58. thread go sell 45
  59. thread run sell 45
  60. thread run sell 43thread go sell 43
  62. thread run sell 41
  63. thread go sell 41
  64. thread go sell 39
  65. thread run sell 39
  66. thread run sell 37
  67. thread go sell 37
  68. thread go sell 35
  69. thread run sell 35
  70. thread go sell 33thread run sell 33
  72. thread go sell 31thread run sell 31
  74. thread go sell 29
  75. thread run sell 29
  76. thread go sell 27
  77. thread run sell 27
  78. thread go sell 25
  79. thread run sell 25
  80. thread run sell 23
  81. thread go sell 23
  82. thread run sell 21
  83. thread go sell 21
  84. thread go sell 19
  85. thread run sell 19
  86. thread run sell 17
  87. thread go sell 17
  88. thread go sell 15
  89. thread run sell 15
  90. thread run sell 13
  91. thread go sell 13
  92. thread run sell 11thread go sell 11
  94. thread go sell 9
  95. thread run sell 9
  96. thread run sell 7
  97. thread go sell 7
  98. thread go sell 5thread run sell 5
  100. thread go sell 3
  101. thread run sell 3
  102. thread go sell 1
  103. thread run sell 1


可以看到，有的票卖了两次，有的票就没卖。

4.注意

1.Sleep()函数是使得线程休眠的函数，这个函数不跨平台，仅仅在windows上能用，其他平台使用usleep。

2.在非主线程中不能使用cocos2d-x管理内存的CCObject::retain(),CCObject::release() 者CCObject::autorelease()，因为CCAutoreleasePool不是线程安全的，OPENGL的上下文也不是线程安全的，所以不要再非主线程中使用cocos2d-x的API和UI操作。


最后工程的源代码下载：http://download.csdn.net/detail/zhy_cheng/5600979

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