Increase device screen brightness

See more:

Mobile

Android

Hi,
I am new to android. Today i create a small android app, in which i have to change the screen brightness of the device.
i am using the following code (got from goggling). and also add permission in manifest file. when executing this code,brightness level in the notification area becomes full.but screen brightness have no changes. how can i fix it? please help me.

code in activity.java

if(iBlank == 0){ 	
               	
               	try {
			curBrightnessValue=android.provider.Settings.System.getInt(getContentResolver(),  android.provider.Settings.System.SCREEN_BRIGHTNESS);
			android.provider.Settings.System.putInt(getContentResolver(), android.provider.Settings.System.SCREEN_BRIGHTNESS,255);
				} 
catch (SettingNotFoundException e) {
				
				}
               }
               else {               	 
               	android.provider.Settings.System.putInt(getContentResolver(), android.provider.Settings.System.SCREEN_BRIGHTNESS,(int)curBrightnessValue);
               }

Permission in manifest file:

<uses-sdk
       android:minSdkVersion="8"
       android:targetSdkVersion="14" />

   <uses-permission android:name="android.permission.WRITE_SETTINGS"></uses-permission>