今天终于算初步写好了一个调节系统背光亮度Brightness的代码，本来不看Android源代码以为可以直接调用某个Action来启动系统的那个调节Brightness的对话框，但是看了代码后发现系统调节Brightness的自定义组件BrightnessPreference继承了SeekBarDialogPreference，但是最终父类还是Preference，因此不能够单独启动，必须得将这个自定义的BrightnessPreference用某个Activity才能加载过来，毕竟最终还是一个组件。因此，将系统的BrightnessPreference改写成Activity的形式，然后将Activity的主题设置为对话框的主题即可。
下图是系统自带的对话框，我的Activity就是仿造这个界面做的。
下面是我改写完后的代码，可以和系统设置的背光设置进行同步，即数据同步，无论是使用自己的Activity还是系统自带的调节背光的亮度，都是一样的效果。代码在Eclipse中运行可能会报错，但是别怕，使用Android编译能通过，然后push到Android设备中去运行没有错误。
代码如下：BrightnessDialogActivity.java
import android.app.Activity;import android.content.ContentResolver;import android.database.ContentObserver;import android.os.Bundle;import android.os.Handler;import android.os.IPowerManager;import android.os.RemoteException;import android.os.ServiceManager;import android.provider.Settings;import android.provider.Settings.SettingNotFoundException;import android.view.View;import android.view.View.OnClickListener;import android.widget.Button;import android.widget.CheckBox;import android.widget.CompoundButton;import android.widget.SeekBar;import com.android.settings.R;import com.canplay.systemui.QuickSettings;import com.canplay.util.DLog;/** * @author ouyangpeng */public class BrightnessDialogActivity extends Activity implements SeekBar.OnSeekBarChangeListener, OnClickListener { private static String TAG="@@@@@@@@@@@@Brightness---->"; private SeekBar mSeekBar; private CheckBox mCheckBox; private Button btnCancel; private Button btnSure; private int mOldBrightness; private int mOldAutomatic; private boolean mAutomaticAvailable; private boolean mAutomaticMode; private int mCurBrightness = -1; private boolean mRestoredOldState; // Backlight range is from 0 - 255. Need to make sure that user // doesn't set the backlight to 0 and get stuck private int mScreenBrightnessDim = android.os.PowerManager.BRIGHTNESS_DIM + 10; private static final int MAXIMUM_BACKLIGHT = android.os.PowerManager.BRIGHTNESS_ON; private static final int SEEK_BAR_RANGE = 10000; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.brightness_dialog_activity); getContentResolver().registerContentObserver( Settings.System.getUriFor(Settings.System.SCREEN_BRIGHTNESS), true, mBrightnessObserver); getContentResolver() .registerContentObserver( Settings.System .getUriFor(Settings.System.SCREEN_BRIGHTNESS_MODE), true, mBrightnessModeObserver); mRestoredOldState = false; mAutomaticAvailable = true; /* * mAutomaticAvailable = getResources() .getBoolean( * com.android.internal.R.bool.config_automatic_brightness_available); */ // mAutomaticAvailable=getBrightnessMode(0)==Settings.System.SCREEN_BRIGHTNESS_MODE_AUTOMATIC; mSeekBar = (SeekBar) findViewById(R.id.brightnessSeekbar); mSeekBar.setMax(SEEK_BAR_RANGE); mOldBrightness = getBrightness(); mSeekBar.setProgress(mOldBrightness); mCheckBox = (CheckBox) findViewById(R.id.brightness_automatic_mode); // 重新读取配置信息 // onBrightnessChanged(); // onBrightnessModeChanged(); if (mAutomaticAvailable) { mCheckBox .setOnCheckedChangeListener(new CheckBox.OnCheckedChangeListener() { @Override public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) { setMode(isChecked ? Settings.System.SCREEN_BRIGHTNESS_MODE_AUTOMATIC : Settings.System.SCREEN_BRIGHTNESS_MODE_MANUAL); mSeekBar.setProgress(getBrightness()); mSeekBar.setEnabled(!mAutomaticMode); setBrightness(mSeekBar.getProgress(), false); } }); mOldAutomatic = getBrightnessMode(0); mAutomaticMode = mOldAutomatic == Settings.System.SCREEN_BRIGHTNESS_MODE_AUTOMATIC; mCheckBox.setChecked(mAutomaticMode); mSeekBar.setEnabled(!mAutomaticMode); } else { mSeekBar.setEnabled(true); } mSeekBar.setOnSeekBarChangeListener(this); btnSure = (Button) findViewById(R.id.btnSure); btnSure.setOnClickListener(this); btnCancel = (Button) findViewById(R.id.btnCancel); btnCancel.setOnClickListener(this); } private ContentObserver mBrightnessObserver = new ContentObserver( new Handler()) { @Override public void onChange(boolean selfChange) { mCurBrightness = -1; onBrightnessChanged(); } }; private ContentObserver mBrightnessModeObserver = new ContentObserver( new Handler()) { @Override public void onChange(boolean selfChange) { onBrightnessModeChanged(); } }; private void onBrightnessChanged() { mSeekBar.setProgress(getBrightness()); } private void onBrightnessModeChanged() { boolean checked = getBrightnessMode(0) == Settings.System.SCREEN_BRIGHTNESS_MODE_AUTOMATIC; mCheckBox.setChecked(checked); mSeekBar.setProgress(getBrightness()); mSeekBar.setEnabled(!checked); } private int getBrightnessMode(int defaultValue) { int brightnessMode = defaultValue; try { brightnessMode = Settings.System.getInt(getContentResolver(), Settings.System.SCREEN_BRIGHTNESS_MODE); } catch (SettingNotFoundException snfe) { } return brightnessMode; } private int getBrightness() { int mode = getBrightnessMode(0); float brightness = 0; if (mode == Settings.System.SCREEN_BRIGHTNESS_MODE_AUTOMATIC) { brightness = Settings.System.getFloat(getContentResolver(), Settings.System.SCREEN_AUTO_BRIGHTNESS_ADJ, 0); brightness = (brightness + 1) / 2; } else { if (mCurBrightness < 0) { brightness = Settings.System.getInt(getContentResolver(), Settings.System.SCREEN_BRIGHTNESS, 100); } else { brightness = mCurBrightness; } brightness = (brightness - mScreenBrightnessDim) / (MAXIMUM_BACKLIGHT - mScreenBrightnessDim); } return (int) (brightness * SEEK_BAR_RANGE); } @Override public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) { setBrightness(progress, false); } @Override public void onStartTrackingTouch(SeekBar seekBar) { } @Override public void onStopTrackingTouch(SeekBar seekBar) { } private void setMode(int mode) { mAutomaticMode = mode == Settings.System.SCREEN_BRIGHTNESS_MODE_AUTOMATIC; Settings.System.putInt(getContentResolver(), Settings.System.SCREEN_BRIGHTNESS_MODE, mode); } private void setBrightness(int brightness, boolean write) { if (mAutomaticMode) { float valf = (((float) brightness * 2) / SEEK_BAR_RANGE) - 1.0f; try { IPowerManager power = IPowerManager.Stub .asInterface(ServiceManager.getService("power")); if (power != null) { power.setAutoBrightnessAdjustment(valf); } if (write) { final ContentResolver resolver = getContentResolver(); Settings.System.putFloat(resolver, Settings.System.SCREEN_AUTO_BRIGHTNESS_ADJ, valf); } } catch (RemoteException doe) { } } else { int range = (MAXIMUM_BACKLIGHT - mScreenBrightnessDim); brightness = (brightness * range) / SEEK_BAR_RANGE + mScreenBrightnessDim; try { IPowerManager power = IPowerManager.Stub .asInterface(ServiceManager.getService("power")); if (power != null) { power.setBacklightBrightness(brightness); } if (write) { mCurBrightness = -1; final ContentResolver resolver = getContentResolver(); Settings.System.putInt(resolver, Settings.System.SCREEN_BRIGHTNESS, brightness); } else { mCurBrightness = brightness; } } catch (RemoteException doe) { } } } private void restoreOldState() { if (mRestoredOldState) return; if (mAutomaticAvailable) { setMode(mOldAutomatic); } setBrightness(mOldBrightness, false); mRestoredOldState = true; mCurBrightness = -1; } @Override public void onClick(View v) { final ContentResolver resolver = getContentResolver(); if (v == findViewById(R.id.btnSure)) { setBrightness(mSeekBar.getProgress(), true); this.finish(); } else if (v == findViewById(R.id.btnCancel)) { restoreOldState(); this.finish(); } resolver.unregisterContentObserver(mBrightnessObserver); resolver.unregisterContentObserver(mBrightnessModeObserver); }} 相应的布局文件如下：brightness_dialog_activity.xml
注册Activity的时候使用下面的主题
android:theme="@android:style/Theme.Holo.Dialog"
但是有个bug，即调用系统的应用调节背光的时候，Seekbar的值和复选框是否被勾中在我的自定义Activity中的Seekbar的值和复选框是否被勾中同步，但是反过来就不行了。
再次读取系统的BrightnessPreference发现是因为没有去进行更新操作。因此得修改Android的源代码，重新编译后才能达到两边数据随便那边修改后，两边的数据都同步。
修改如下所示，修改前BrightnessPreference.showDialog(Bundle state)
@Override protected void showDialog(Bundle state) { super.showDialog(state); getContext().getContentResolver().registerContentObserver( Settings.System.getUriFor(Settings.System.SCREEN_BRIGHTNESS), true, mBrightnessObserver); getContext().getContentResolver().registerContentObserver( Settings.System.getUriFor(Settings.System.SCREEN_BRIGHTNESS_MODE), true, mBrightnessModeObserver); mRestoredOldState = false; } 修改后BrightnessPreference.showDialog(Bundle state)，即打开对话框的时候重新去读取数据库里面的Brightness的值和复选框是否被选中的值。
@Override protected void showDialog(Bundle state) { super.showDialog(state); getContext().getContentResolver().registerContentObserver( Settings.System.getUriFor(Settings.System.SCREEN_BRIGHTNESS), true, mBrightnessObserver); getContext().getContentResolver().registerContentObserver( Settings.System.getUriFor(Settings.System.SCREEN_BRIGHTNESS_MODE), true, mBrightnessModeObserver); onBrightnessChanged(); onBrightnessModeChanged(); mRestoredOldState = false; } ====================================================================================
作者：欧阳鹏 欢迎转载，与人分享是进步的源泉！
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最后附上系统调节Brightness的代码
/* * Copyright (C) 2008 The Android Open Source Project * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */package com.android.settings;import android.content.ContentResolver;import android.content.Context;import android.database.ContentObserver;import android.os.Bundle;import android.os.Handler;import android.os.IPowerManager;import android.os.Parcel;import android.os.Parcelable;import android.os.RemoteException;import android.os.ServiceManager;import android.preference.SeekBarDialogPreference;import android.provider.Settings;import android.provider.Settings.SettingNotFoundException;import android.util.AttributeSet;import android.view.View;import android.widget.CheckBox;import android.widget.CompoundButton;import android.widget.SeekBar;public class BrightnessPreference extends SeekBarDialogPreference implements SeekBar.OnSeekBarChangeListener, CheckBox.OnCheckedChangeListener { private SeekBar mSeekBar; private CheckBox mCheckBox; private int mOldBrightness; private int mOldAutomatic; private boolean mAutomaticAvailable; private boolean mAutomaticMode; private int mCurBrightness = -1; private boolean mRestoredOldState; // Backlight range is from 0 - 255. Need to make sure that user // doesn't set the backlight to 0 and get stuck private int mScreenBrightnessDim = getContext().getResources().getInteger(com.android.internal.R.integer.config_screenBrightnessDim); private static final int MAXIMUM_BACKLIGHT = android.os.PowerManager.BRIGHTNESS_ON; private static final int SEEK_BAR_RANGE = 10000; private ContentObserver mBrightnessObserver = new ContentObserver(new Handler()) { @Override public void onChange(boolean selfChange) { mCurBrightness = -1; onBrightnessChanged(); } }; private ContentObserver mBrightnessModeObserver = new ContentObserver(new Handler()) { @Override public void onChange(boolean selfChange) { onBrightnessModeChanged(); } }; public BrightnessPreference(Context context, AttributeSet attrs) { super(context, attrs); mAutomaticAvailable = context.getResources().getBoolean( com.android.internal.R.bool.config_automatic_brightness_available); setDialogLayoutResource(R.layout.preference_dialog_brightness); setDialogIcon(R.drawable.ic_settings_display); } @Override protected void showDialog(Bundle state) { super.showDialog(state); getContext().getContentResolver().registerContentObserver( Settings.System.getUriFor(Settings.System.SCREEN_BRIGHTNESS), true, mBrightnessObserver); getContext().getContentResolver().registerContentObserver( Settings.System.getUriFor(Settings.System.SCREEN_BRIGHTNESS_MODE), true, mBrightnessModeObserver); onBrightnessChanged(); onBrightnessModeChanged(); mRestoredOldState = false; } @Override protected void onBindDialogView(View view) { super.onBindDialogView(view); mSeekBar = getSeekBar(view); mSeekBar.setMax(SEEK_BAR_RANGE); mOldBrightness = getBrightness(); mSeekBar.setProgress(mOldBrightness); mCheckBox = (CheckBox)view.findViewById(R.id.automatic_mode); if (mAutomaticAvailable) { mCheckBox.setOnCheckedChangeListener(this); mOldAutomatic = getBrightnessMode(0); mAutomaticMode = mOldAutomatic == Settings.System.SCREEN_BRIGHTNESS_MODE_AUTOMATIC; mCheckBox.setChecked(mAutomaticMode); mSeekBar.setEnabled(!mAutomaticMode); } else { mSeekBar.setEnabled(true); } mSeekBar.setOnSeekBarChangeListener(this); } public void onProgressChanged(SeekBar seekBar, int progress, boolean fromTouch) { setBrightness(progress, false); } public void onStartTrackingTouch(SeekBar seekBar) { // NA } public void onStopTrackingTouch(SeekBar seekBar) { // NA } public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) { setMode(isChecked ? Settings.System.SCREEN_BRIGHTNESS_MODE_AUTOMATIC : Settings.System.SCREEN_BRIGHTNESS_MODE_MANUAL); mSeekBar.setProgress(getBrightness()); mSeekBar.setEnabled(!mAutomaticMode); setBrightness(mSeekBar.getProgress(), false); } private int getBrightness() { int mode = getBrightnessMode(0); float brightness = 0; if (false && mode == Settings.System.SCREEN_BRIGHTNESS_MODE_AUTOMATIC) { brightness = Settings.System.getFloat(getContext().getContentResolver(), Settings.System.SCREEN_AUTO_BRIGHTNESS_ADJ, 0); brightness = (brightness+1)/2; } else { if (mCurBrightness < 0) { brightness = Settings.System.getInt(getContext().getContentResolver(), Settings.System.SCREEN_BRIGHTNESS, 100); } else { brightness = mCurBrightness; } brightness = (brightness - mScreenBrightnessDim) / (MAXIMUM_BACKLIGHT - mScreenBrightnessDim); } return (int)(brightness*SEEK_BAR_RANGE); } private int getBrightnessMode(int defaultValue) { int brightnessMode = defaultValue; try { brightnessMode = Settings.System.getInt(getContext().getContentResolver(), Settings.System.SCREEN_BRIGHTNESS_MODE); } catch (SettingNotFoundException snfe) { } return brightnessMode; } private void onBrightnessChanged() { mSeekBar.setProgress(getBrightness()); } private void onBrightnessModeChanged() { boolean checked = getBrightnessMode(0) == Settings.System.SCREEN_BRIGHTNESS_MODE_AUTOMATIC; mCheckBox.setChecked(checked); mSeekBar.setProgress(getBrightness()); mSeekBar.setEnabled(!checked); } @Override protected void onDialogClosed(boolean positiveResult) { super.onDialogClosed(positiveResult); final ContentResolver resolver = getContext().getContentResolver(); if (positiveResult) { setBrightness(mSeekBar.getProgress(), true); } else { restoreOldState(); } resolver.unregisterContentObserver(mBrightnessObserver); resolver.unregisterContentObserver(mBrightnessModeObserver); } private void restoreOldState() { if (mRestoredOldState) return; if (mAutomaticAvailable) { setMode(mOldAutomatic); } setBrightness(mOldBrightness, false); mRestoredOldState = true; mCurBrightness = -1; } private void setBrightness(int brightness, boolean write) { if (mAutomaticMode) { if (false) { float valf = (((float)brightness*2)/SEEK_BAR_RANGE) - 1.0f; try { IPowerManager power = IPowerManager.Stub.asInterface( ServiceManager.getService("power")); if (power != null) { power.setAutoBrightnessAdjustment(valf); } if (write) { final ContentResolver resolver = getContext().getContentResolver(); Settings.System.putFloat(resolver, Settings.System.SCREEN_AUTO_BRIGHTNESS_ADJ, valf); } } catch (RemoteException doe) { } } } else { int range = (MAXIMUM_BACKLIGHT - mScreenBrightnessDim); brightness = (brightness*range)/SEEK_BAR_RANGE + mScreenBrightnessDim; try { IPowerManager power = IPowerManager.Stub.asInterface( ServiceManager.getService("power")); if (power != null) { power.setBacklightBrightness(brightness); } if (write) { mCurBrightness = -1; final ContentResolver resolver = getContext().getContentResolver(); Settings.System.putInt(resolver, Settings.System.SCREEN_BRIGHTNESS, brightness); } else { mCurBrightness = brightness; } } catch (RemoteException doe) { } } } private void setMode(int mode) { mAutomaticMode = mode == Settings.System.SCREEN_BRIGHTNESS_MODE_AUTOMATIC; Settings.System.putInt(getContext().getContentResolver(), Settings.System.SCREEN_BRIGHTNESS_MODE, mode); } @Override protected Parcelable onSaveInstanceState() { final Parcelable superState = super.onSaveInstanceState(); if (getDialog() == null || !getDialog().isShowing()) return superState; // Save the dialog state final SavedState myState = new SavedState(superState); myState.automatic = mCheckBox.isChecked(); myState.progress = mSeekBar.getProgress(); myState.oldAutomatic = mOldAutomatic == 1; myState.oldProgress = mOldBrightness; myState.curBrightness = mCurBrightness; // Restore the old state when the activity or dialog is being paused restoreOldState(); return myState; } @Override protected void onRestoreInstanceState(Parcelable state) { if (state == null || !state.getClass().equals(SavedState.class)) { // Didn't save state for us in onSaveInstanceState super.onRestoreInstanceState(state); return; } SavedState myState = (SavedState) state; super.onRestoreInstanceState(myState.getSuperState()); mOldBrightness = myState.oldProgress; mOldAutomatic = myState.oldAutomatic ? 1 : 0; setMode(myState.automatic ? 1 : 0); setBrightness(myState.progress, false); mCurBrightness = myState.curBrightness; } private static class SavedState extends BaseSavedState { boolean automatic; boolean oldAutomatic; int progress; int oldProgress; int curBrightness; public SavedState(Parcel source) { super(source); automatic = source.readInt() == 1; progress = source.readInt(); oldAutomatic = source.readInt() == 1; oldProgress = source.readInt(); curBrightness = source.readInt(); } @Override public void writeToParcel(Parcel dest, int flags) { super.writeToParcel(dest, flags); dest.writeInt(automatic ? 1 : 0); dest.writeInt(progress); dest.writeInt(oldAutomatic ? 1 : 0); dest.writeInt(oldProgress); dest.writeInt(curBrightness); } public SavedState(Parcelable superState) { super(superState); } public static final Parcelable.Creator CREATOR = new Parcelable.Creator () { public SavedState createFromParcel(Parcel in) { return new SavedState(in); } public SavedState[] newArray(int size) { return new SavedState[size]; } }; }}