Android Android屏幕亮度设置

求教关于Android屏幕亮度调节的问题，屏幕亮度分两种，一种是系统的，一种是局限于应用内的，我希望是应用内的调节即可，一款读书软件。

现在有这么几种思路，也是在网上找的，居然都不可以，不知道为什么

一种是

1\. private void brightnessMax() {
   2. WindowManager.LayoutParams lp = getWindow().getAttributes();
   3. lp.screenBrightness = 1.0f;
   4. getWindow().setAttributes(lp);
   5. }

再详细一点是

public class MyActivity extends Activity {
        /** Called when the activity is first created. */
        TextView textView;
 
        @Override
        public void onCreate(Bundle savedInstanceState) {
                super.onCreate(savedInstanceState);
                setContentView(R.layout.main);
                textView = (TextView) findViewById(R.id.MyTextView);
                updateToggles();
        }
 
        private void updateToggles() {
                // TODO Auto-generated method stub
                SeekBar seekBar = (SeekBar) findViewById(R.id.MySeekBar);
                seekBar.setProgress((int) (android.provider.Settings.System.getInt(
                                getContentResolver(),
                                android.provider.Settings.System.SCREEN_BRIGHTNESS, 255) ));
                seekBar.setOnSeekBarChangeListener(seekListener);
        }
 
        private OnSeekBarChangeListener seekListener = new OnSeekBarChangeListener() {
 
                public void onProgressChanged(SeekBar seekBar, int progress,
                                boolean fromUser) {
                        if (fromUser) {
                                Integer tmpInt = seekBar.getProgress();
                                System.out.println(tmpInt);
                                // 51 (seek scale) * 5 = 255 (max brightness)
                                // Old way
                                android.provider.Settings.System.putInt(getContentResolver(),
                                                android.provider.Settings.System.SCREEN_BRIGHTNESS,
                                                tmpInt); // 0-255
                                tmpInt = Settings.System.getInt(getContentResolver(),
                                               Settings.System.SCREEN_BRIGHTNESS, -1);
                                // Cupcake way..... sucks
                                WindowManager.LayoutParams lp = getWindow().getAttributes();
                                // lp.screenBrightness = 1.0f;
                                // Float tmpFloat = (float)tmpInt / 255;
                                if (0<= tmpInt && tmpInt <= 255) {
                                        lp.screenBrightness = tmpInt;
                                }
                                 
                                 
                                getWindow().setAttributes(lp);
                        }
 
                }
 
                @Override
                public void onStartTrackingTouch(SeekBar seekBar) {
                        // TODO Auto-generated method stub
                        // put awesomeness here
                }
 
                @Override
                public void onStopTrackingTouch(SeekBar seekBar) {
                        // TODO Auto-generated method stub
                        // and here too
                }
        };
}这是主程序

http://stackoverflow.com/questions/4544967/get-preferred-screen-brightness-in-android