Android 调节当前Activity的屏幕亮度

调节的关键代码：

        WindowManager.LayoutParams layoutParams = getWindow().getAttributes();
        layoutParams.screenBrightness = Float.parseFloat(brightNum);
        getWindow().setAttributes(layoutParams);

以下是一个例子，包含拖动条控件：

布局文件：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
              android:orientation="vertical"
              android:layout_width="fill_parent"
              android:layout_height="fill_parent"
        >

    <EditText
            android:id="@+id/et"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:hint="请输入亮度（0-1）"
            />

    <Button
            android:id="@+id/btn_set"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="设置一下当前亮度"
            android:onClick="changeBright"
            />

    <Button
            android:id="@+id/btn_set"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="设置一下当前亮度 [0, 1]"
            android:onClick="changeBright2"
            />

    <Button
            android:id="@+id/btn_current"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_marginTop="10dp"
            android:text="获取当前亮度（非自动调节模式生效）"
            android:onClick="showCurrentBright"
            />

    <SeekBar
            android:id="@+id/seek_bar"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"

            />

    <Button android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="设置为自动调节屏幕亮度"
            android:onClick="setAutoBright"
            />

    <Button android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="设置为手动调节屏幕亮度"
            android:onClick="setManualBright"
            />

    <Button android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="获取亮度的模式（与系统设置相关）"
            android:onClick="showScreenMode"
            />

    <Button android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="让手机直接黑屏..."
            android:onClick="setNoBright"
            />
</LinearLayout>

Activity：

package com.example.screenBrightnessTest;

import android.app.Activity;
import android.content.ContentResolver;
import android.os.Bundle;
import android.provider.Settings;
import android.view.View;
import android.view.WindowManager;
import android.widget.EditText;
import android.widget.SeekBar;
import android.widget.Toast;

public class MyActivity extends Activity {
    private EditText editText;
    private SeekBar seekBar;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        editText = (EditText) findViewById(R.id.et);
        seekBar = (SeekBar) findViewById(R.id.seek_bar);

        //设置滚动条
        seekBar.setProgress(getCurrentBrightValue());
        seekBar.setMax(255);
        seekBar.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {
            /**
             * 拖动中数值的时候
             * @param fromUser 是否是由用户操作的
             */
            @Override
            public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {
                if (progress > 3 && fromUser) {//以免太暗
                    WindowManager.LayoutParams layoutParams = getWindow().getAttributes();
                    layoutParams.screenBrightness = (float) progress / 255;//因为这个值是[0, 1]范围的
                    getWindow().setAttributes(layoutParams);
                }
            }

            /**
             * 当按下的时候
             */
            @Override
            public void onStartTrackingTouch(SeekBar seekBar) {
                System.out.println("com.example.screenBrightnessTest.MyActivity.onStartTrackingTouch");
            }

            /**
             *当松开的时候
             */
            @Override
            public void onStopTrackingTouch(SeekBar seekBar) {
                System.out.println("com.example.screenBrightnessTest.MyActivity.onStopTrackingTouch");
            }
        });
    }

    public void changeBright(View view) {
        String brightNum = editText.getText().toString();
        WindowManager.LayoutParams layoutParams = getWindow().getAttributes();
        layoutParams.screenBrightness = Float.parseFloat(brightNum);
        getWindow().setAttributes(layoutParams);
    }

    /**
     * 仅当系统的亮度模式是非自动模式的情况下，获取当前屏幕亮度值[0, 255].
     * 如果是自动模式，那么该方法获得的值不正确。
     */
    private int getCurrentBrightValue() {
        int nowBrightnessValue = 0;
        ContentResolver resolver = getContentResolver();
        try {
            nowBrightnessValue = android.provider.Settings.System.getInt(resolver,
                    Settings.System.SCREEN_BRIGHTNESS, 255);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return nowBrightnessValue;
    }

    /**
     * 获取当前的亮度
     */
    private float getMaxBrightValue2() {
        return getWindow().getAttributes().screenBrightness;
    }

    public void showCurrentBright(View view) {
        Toast.makeText(this, "当前系统亮度的值为：" + getCurrentBrightValue(), 1).show();
    }

    /**
     * 让手机直接黑屏
     */
    public void setNoBright(View view) {
        getWindow().getAttributes().screenBrightness = 0;
    }

    /**
     * 设置当前屏幕亮度的模式
     *
     * @param paramInt Settings.System.SCREEN_BRIGHTNESS_MODE_AUTOMATIC或者Settings.System.SCREEN_BRIGHTNESS_MODE_MANUAL
     */
    private void setScreenMode(int paramInt) {
        try {
            Settings.System.putInt(getContentResolver(), Settings.System.SCREEN_BRIGHTNESS_MODE, paramInt);
        } catch (Exception localException) {
            localException.printStackTrace();
        }
    }

    /**
     * 设置为自动调节亮度
     * 如果当前系统的模式不是自动调节模式，那么才会生效
     */
    public void setAutoBright(View view) {
        setScreenMode(Settings.System.SCREEN_BRIGHTNESS_MODE_AUTOMATIC);
    }

    /**
     * 获得当前屏幕亮度的模式
     */
    public void showScreenMode(View view) {
        int screenMode = 0;
        try {
            screenMode = Settings.System.getInt(getContentResolver(), Settings.System.SCREEN_BRIGHTNESS_MODE);
            switch (screenMode) {
                case Settings.System.SCREEN_BRIGHTNESS_MODE_AUTOMATIC:
                    Toast.makeText(this, "自动亮度模式", 1).show();
                    break;
                default:
                    Toast.makeText(this, "手动调节亮度", 1).show();
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public void setManualBright(View view) {
        setScreenMode(Settings.System.SCREEN_BRIGHTNESS_MODE_MANUAL);
    }

    public void changeBright2(View view) {
        Toast.makeText(this, "亮度值[0, 1] = " + getWindow().getAttributes().screenBrightness, 1).show();
    }

}