How to adjust the brightness of the device from our app in iPad

I am de开发者_Python百科veloping a eBook reader app for iPad and i want to add a feature where in the user can adjust the brightness of the device from the app. Is there anyway in which i can implement this in my app..???

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I found rather a simple solution for it. I am adding a UIVIew of clear color to my book reader view and i am increasing the alpha component of this view upon the slider value changed event. By doing this , my view gets darkened and we get a feeling that the brightness of the app is reduced.. This solution may not be very appropriate, but works just fine in my case. Any better solutions are always appreciated.Thank you...

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well, its not the exact solution, but it will serve the purpose...

 -(IBAction)sliderValueChangedForBrightness:(UISlider*)sliderObj{

    brightnessView.backgroundColor=[[UIColor grayColor] colorWithAlphaComponent:1-sliderObj.value];
}

-(IBAction)adjustBrightness:(UIButton *)sender{   

    if(isbrightnessViewShowing==NO){
        isbrightnessViewShowing=YES;
        [self.view addSubview:brightnessSliderView];
        brightnessSliderView.frame=CGRectMake(sender.frame.origin.x-70,brandingView.frame.size.height, brightnessSliderView.frame.size.width, brightnessSliderView.frame.size.height);
    }
    else {
        isbrightnessViewShowing=NO;
        [brightnessSliderView removeFromSuperview];
    }

    if (brightnessView==nil) {
        brightnessView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, scrollView.frame.size.width, scrollView.frame.size.height)];
        brightnessView.backgroundColor = [UIColor clearColor];
    }

    [webView addSubview:brightnessView];
    [webView bringSubviewToFront:brightnessView];       
}