ios - 无法更改 UIImagePickerController 的 cameraFlashMode

Question

我的自定义相机覆盖上有一个按钮，可以调用此方法：

- (void) changeFlash:(id)sender
{
    //UIImagePickerControllerCameraFlashModeOff  = -1,
    //UIImagePickerControllerCameraFlashModeAuto = 0,
    //UIImagePickerControllerCameraFlashModeOn   = 1
    NSLog(@"before %d", self.picker.cameraFlashMode);
    switch (self.picker.cameraFlashMode) {
        case UIImagePickerControllerCameraFlashModeAuto:
            [(UIButton *)sender setImage:[UIImage imageNamed:@"flashOn"] forState:UIControlStateNormal];
            self.picker.cameraFlashMode = UIImagePickerControllerCameraFlashModeOn;
            break;
        case UIImagePickerControllerCameraFlashModeOn:
            [(UIButton *)sender setImage:[UIImage imageNamed:@"flashOff"] forState:UIControlStateNormal];
            self.picker.cameraFlashMode = UIImagePickerControllerCameraFlashModeOff;
            break;

        case UIImagePickerControllerCameraFlashModeOff:
            [(UIButton *)sender setImage:[UIImage imageNamed:@"flashAuto"] forState:UIControlStateNormal];
            self.picker.cameraFlashMode = UIImagePickerControllerCameraFlashModeAuto;
            break;
    }
    NSLog(@"after %d", self.picker.cameraFlashMode);

}

self.picker.cameraFlashMode 在更改前后始终为 0。我究竟做错了什么？

此外，闪光灯从不工作，即使它据说卡在 UIImagePickerControllerCameraFlashModeAuto 中。

Answer 1

self.picker 为零。这是一个常见的错误，您需要经常检查，因为与 Java 和其他语言不同，在 Objective-C 中向 nil 发送消息是有效的。