从块内更新标签的安全方法？

发布于 2024-10-28 02:39:18 字数 394 浏览 1 评论 0原文

示例：我有这个块，我想更新屏幕上的标签：

[self.motionManager startDeviceMotionUpdatesToQueue:[NSOperationQueue currentQueue] withHandler:^(CMDeviceMotion *deviceMotion, NSError *error) {
        CMAcceleration *userAcceleration = deviceMotion.userAcceleration;
        self.labelX.text = [NSNumber numberWithFormat:@"%f", userAcceleration.x];
     }];

我担心这不会很好地工作。线程问题等？建议？

原文

Example: I have this block, and I want to update a label on the screen:

[self.motionManager startDeviceMotionUpdatesToQueue:[NSOperationQueue currentQueue] withHandler:^(CMDeviceMotion *deviceMotion, NSError *error) {
        CMAcceleration *userAcceleration = deviceMotion.userAcceleration;
        self.labelX.text = [NSNumber numberWithFormat:@"%f", userAcceleration.x];
     }];

I fear this won't work well. Threading-problems, etc? Suggestions?

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娜些时光，永不杰束 2024-11-04 02:39:18

作为比使用 -performSelectorOnMainThread: 更优雅的解决方案，您可以简单地使用一个块来保证 UI 更新在主线程上：

[self.motionManager startDeviceMotionUpdatesToQueue:[NSOperationQueue currentQueue] withHandler:^(CMDeviceMotion *deviceMotion, NSError *error) {
    CMAcceleration *userAcceleration = deviceMotion.userAcceleration;

    dispatch_async(dispatch_get_main_queue(), ^{
        self.labelX.text = [NSString stringWithFormat:@"%f", userAcceleration.x];
    });
}];

请注意，[NSOperationQueue currentQueue] 将返回如果主队列是您运行上述代码的位置，那么在这种情况下您的回调将已经在主队列上运行。

As a more elegant solution than using -performSelectorOnMainThread:, you could simply use a block to guarantee your UI update is on the main thread:

[self.motionManager startDeviceMotionUpdatesToQueue:[NSOperationQueue currentQueue] withHandler:^(CMDeviceMotion *deviceMotion, NSError *error) {
    CMAcceleration *userAcceleration = deviceMotion.userAcceleration;

    dispatch_async(dispatch_get_main_queue(), ^{
        self.labelX.text = [NSString stringWithFormat:@"%f", userAcceleration.x];
    });
}];

Note that [NSOperationQueue currentQueue] will return the main queue if that's where you run the above code from, so your callback will already be running on the main queue in that case.

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