无法更改UIImagePickerController的cameraFlashMode

Question

我的自定义相机覆盖图上有一个按钮，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在更改之前和之后始终为0。我做错了什么？

此外，闪存永远不会工作，即使它被卡在UIImagePickerControllerCameraFlashModeAuto中。

Answer 1

self.picker是零。这是一个常见的错误，您需要经常检查这一点，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。