在播放器中，我们常常可以看到这么一个设计，就是用户通过在屏幕的某个部分上下滑动就可以调节屏幕的亮度，在某个部分上下滑动就可以调节播放的音量。而左右滑动就可以调节播放的进度。

今天，我要说一下亮度的调节。其实主要是通过设置View的属性实现的。

  public void onLightChange(float delta, int distance, Window window) {
        WindowManager.LayoutParams params = window.getAttributes();

        mCurrentDeltaBrintness = mCurrentDeltaBrintness + delta;

        if (params.screenBrightness == WindowManager.LayoutParams.BRIGHTNESS_OVERRIDE_NONE) {
            params.screenBrightness = getScreenBrightness(getContext());
        }

        if (Math.abs(mCurrentDeltaBrintness) >= mScrolledPixPerBringhtness) {
            float deltaBrightness = mCurrentDeltaBrintness / (mScrolledPixPerBringhtness * MAX_BRINTNESS);
            params.screenBrightness = params.screenBrightness + deltaBrightness;
<pre name="code" class="java">    private void performLightChange(float brightness) {
        int resId = R.drawable.light_0;

        if (brightness <= 0.01f) {
            resId = R.drawable.light_0;
        } else if (brightness <= 0.25f) {
            resId = R.drawable.light_25;
        } else if (brightness <= 0.5f) {
            resId = R.drawable.light_50;
        } else if (brightness < 1.0f) {
            resId = R.drawable.light_75;
        } else {
            resId = R.drawable.light_100;
        }

        updateViews(resId, (int) (brightness * 100));
    }

另附performLigthChange的代码。

    private void performLightChange(float brightness) {
        int resId = R.drawable.light_0;

        if (brightness <= 0.01f) {
            resId = R.drawable.light_0;
        } else if (brightness <= 0.25f) {
            resId = R.drawable.light_25;
        } else if (brightness <= 0.5f) {
            resId = R.drawable.light_50;
        } else if (brightness < 1.0f) {
            resId = R.drawable.light_75;
        } else {
            resId = R.drawable.light_100;
        }

        updateViews(resId, (int) (brightness * 100));
    }

复制代码
 1 package android.lekko.tools;
 2 
 3 import android.app.Activity;
 4 import android.content.ContentResolver;
 5 import android.provider.Settings;
 6 import android.provider.Settings.System;
 7 import android.view.WindowManager;
 8 import android.widget.Toast;
 9 
10 public class LightnessControl {
11     // 判断是否开启了自动亮度调节 
12     public static boolean isAutoBrightness(Activity act) { 
13         boolean automicBrightness = false; 
14         ContentResolver aContentResolver = act.getContentResolver();
15         try { 
16             automicBrightness = Settings.System.getInt(aContentResolver, 
17                    Settings.System.SCREEN_BRIGHTNESS_MODE) == Settings.System.SCREEN_BRIGHTNESS_MODE_AUTOMATIC; 
18         } catch (Exception e) { 
19             Toast.makeText(act,"无法获取亮度",Toast.LENGTH_SHORT).show();
20         } 
21         return automicBrightness; 
22     }     
23     // 改变亮度
24     public static void SetLightness(Activity act,int value)
25     {        
26         try {
27             System.putInt(act.getContentResolver(),System.SCREEN_BRIGHTNESS,value); 
28             WindowManager.LayoutParams lp = act.getWindow().getAttributes(); 
29             lp.screenBrightness = (value<=0?1:value) / 255f;
30             act.getWindow().setAttributes(lp);
31         } catch (Exception e) {
32             Toast.makeText(act,"无法改变亮度",Toast.LENGTH_SHORT).show();
33         }        
34     }
35     // 获取亮度
36     public static int GetLightness(Activity act)
37     {
38         return System.getInt(act.getContentResolver(),System.SCREEN_BRIGHTNESS,-1);
39     }
40     // 停止自动亮度调节 
41     public static void stopAutoBrightness(Activity activity) { 
42         Settings.System.putInt(activity.getContentResolver(), 
43                 Settings.System.SCREEN_BRIGHTNESS_MODE, 
44                 Settings.System.SCREEN_BRIGHTNESS_MODE_MANUAL); 
45     }
46     // 开启亮度自动调节 
47     public static void startAutoBrightness(Activity activity) { 
48         Settings.System.putInt(activity.getContentResolver(), 
49                 Settings.System.SCREEN_BRIGHTNESS_MODE, 
50                 Settings.System.SCREEN_BRIGHTNESS_MODE_AUTOMATIC); 
51     } 
52 }
复制代码
　　这是一个单独可工作的类，主要用于调节屏幕亮度，有部分注释了，解释几个概念，不标准，供参考：
　　ContentResolver类，为访问其它应用程序的对外共享数据提供方法，如上面获取、设置亮度时使用的System.getInt()，System.setInt()。
　　Activity类，android程序的主要类，一个界面必有此类提供后台支持，需要继承此类。
　　Settings类，android程序系统相关的设置类，各种设置都可在此找。
　　LayoutParams类，android界面相关的参数，如高度、宽度、亮度等。
　　Toast类，一个可自动消失的提示框，轻型控件。

Android开发之调节屏幕亮度