IOHIDEventSystemClientScheduleWithRunLoop与EXC_BAD_ACCESS

问题描述

我正在尝试在我的应用程序中获取触摸事件。所以我使用IOHIDFamily回调来获取事件。我的代码是这样的：

I'm trying to get touch events in my application. So I used the IOHIDFamily callback to get the events. My code is like this:

void handle_event(void* target, void* refcon, IOHIDServiceRef service, IOHIDEventRef event)
{
    printf("Received event of type %2d from service %p.\n",
           IOHIDEventGetType(event), service);
}

- (void)viewDidLoad
{
    [super viewDidLoad];

    void *ioHIDEventSystem = IOHIDEventSystemClientCreate(kCFAllocatorDefault);
    IOHIDEventSystemClientScheduleWithRunLoop(system, CFRunLoopGetCurrent(), kCFRunLoopDefaultMode);
    IOHIDEventSystemClientRegisterEventCallback(system, handle_event, NULL, NULL);
    CFRunLoopRun();
}

执行时出错：

IOKit`IOHIDEventSystemClientScheduleWithRunLoop：

...

0x32f8fd14：cmp.w r10，＃0

0x32f8fd18：strd r10，r11，[r4，＃116]< --- EXC_BAD_ACCESS（代码= EXC_ARM_DA_ALIGN）

0x32f8fd1c：beq 0x32f8fdac; IOHIDEventSystemClientScheduleWithRunLoop + 168

0x32f8fd1e：ldr r1，[r4，＃96]

0x32f8fd20：cbz r1,0x32f8fd2a; IOHIDEventSystemClientScheduleWithRunLoop + 38

0x32f8fd22：mov r0，r10

...

IOKit`IOHIDEventSystemClientScheduleWithRunLoop:
...
0x32f8fd14: cmp.w r10, #0
0x32f8fd18: strd r10, r11, [r4, #116] <---EXC_BAD_ACCESS(code=EXC_ARM_DA_ALIGN)
0x32f8fd1c: beq 0x32f8fdac ; IOHIDEventSystemClientScheduleWithRunLoop + 168
0x32f8fd1e: ldr r1, [r4, #96]
0x32f8fd20: cbz r1, 0x32f8fd2a ; IOHIDEventSystemClientScheduleWithRunLoop + 38
0x32f8fd22: mov r0, r10
...

我以错误的方式使用IOHIDFamily？

Did I use IOHIDFamily in the wrong way?

推荐答案

我发现代码中至少有几个问题：

There's at least a couple problems I see in the code posted:

首先，您正在致电

CFRunLoopRun();

$ b

在 viewDidLoad 方法中在main / UI线程上调用。我认为没有理由，所以只需删除该行。我通常希望看到那个调用，如果你有一个方法，你在后台线程上运行，你需要启动后台运行循环。或者，如果您直接在 main（）中注册回调，请。

in the viewDidLoad method, which is going to be called on the main/UI thread. I see no reason for that, so just remove that line. I'd normally expect to see that call if you had a method that you were running on a background thread, and you needed to start a background run loop. Or, if you were registering for callbacks directly in main(), as in this answer.

然后，你有这个：

void *ioHIDEventSystem = IOHIDEventSystemClientCreate(kCFAllocatorDefault);
IOHIDEventSystemClientScheduleWithRunLoop(system, CFRunLoopGetCurrent(), kCFRunLoopDefaultMode);

我猜第二行应该是

IOHIDEventSystemClientScheduleWithRunLoop(ioHIDEventSystem, CFRunLoopGetCurrent(), kCFRunLoopDefaultMode);

我不知道系统是什么变量实际上是指，但它看起来不正确。

I don't know what the system variable actually refers to, but it doesn't look right.

参加，因为它似乎正确使用 IOKit 。

Take a look at this recent answer, as it seems to use IOKit correctly.

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