Android系统设置亮度实现流程

　

public class BrightnessPreference extends Preference {    public BrightnessPreference(Context context, AttributeSet attrs) {        super(context, attrs);    }    @Override    protected void onClick() {        getContext().startActivityAsUser(new Intent(Intent.ACTION_SHOW_BRIGHTNESS_DIALOG),                UserHandle.CURRENT_OR_SELF);    }}

 

 　SystemUI  AndroidManifest.xml 注册了

 <activity
            android:name=".settings.BrightnessDialog"
            android:label="@string/quick_settings_brightness_dialog_title"
            android:theme="@android:style/Theme.DeviceDefault.Dialog"
            android:finishOnCloseSystemDialogs="true"
            android:launchMode="singleInstance"
            android:excludeFromRecents="true"
            android:exported="true">
            <intent-filter>
                <action android:name="android.intent.action.SHOW_BRIGHTNESS_DIALOG" />
                <category android:name="android.intent.category.DEFAULT" />
            </intent-filter>
        </activity>

 

 　由BrightnessDialog new 一个BrightnessController。

 

public class BrightnessController implements ToggleSlider.Listener {
    private static final String TAG = "StatusBar.BrightnessController";
    private static final boolean SHOW_AUTOMATIC_ICON = false;


    /**
     * {@link android.provider.Settings.System#SCREEN_AUTO_BRIGHTNESS_ADJ} uses the range [-1, 1].
     * Using this factor, it is converted to [0, BRIGHTNESS_ADJ_RESOLUTION] for the SeekBar.
     */
    private static final float BRIGHTNESS_ADJ_RESOLUTION = 100;


    private final int mMinimumBacklight;
    private final int mMaximumBacklight;


    private final Context mContext;
    private final ImageView mIcon;
    private final ToggleSlider mControl;
    private final boolean mAutomaticAvailable;
    private final IPowerManager mPower;
    private final CurrentUserTracker mUserTracker;
    private final Handler mHandler;
    private final BrightnessObserver mBrightnessObserver;


    private ArrayList<BrightnessStateChangeCallback> mChangeCallbacks =
            new ArrayList<BrightnessStateChangeCallback>();


    private boolean mAutomatic;
    private boolean mListening;
    private boolean mExternalChange;


    public interface BrightnessStateChangeCallback {
        public void onBrightnessLevelChanged();
    }


    /** 观察者模式，观察对应的URI是否有变化**/
    private class BrightnessObserver extends ContentObserver {


        private final Uri BRIGHTNESS_MODE_URI =
                Settings.System.getUriFor(Settings.System.SCREEN_BRIGHTNESS_MODE);
        private final Uri BRIGHTNESS_URI =
                Settings.System.getUriFor(Settings.System.SCREEN_BRIGHTNESS);
        private final Uri BRIGHTNESS_ADJ_URI =
                Settings.System.getUriFor(Settings.System.SCREEN_AUTO_BRIGHTNESS_ADJ);


        public BrightnessObserver(Handler handler) {
            super(handler);
        }


        @Override
        public void onChange(boolean selfChange) {
            onChange(selfChange, null);
        }


        @Override
        public void onChange(boolean selfChange, Uri uri) {
            if (selfChange) return;
            try {
                mExternalChange = true;
                if (BRIGHTNESS_MODE_URI.equals(uri)) {
                    updateMode();
                    updateSlider();
                } else if (BRIGHTNESS_URI.equals(uri) && !mAutomatic) {
                    updateSlider();
                } else if (BRIGHTNESS_ADJ_URI.equals(uri) && mAutomatic) {
                    updateSlider();
                } else {
                    updateMode();
                    updateSlider();
                }
                for (BrightnessStateChangeCallback cb : mChangeCallbacks) {
                    cb.onBrightnessLevelChanged();
                }
            } finally {
                mExternalChange = false;
            }
        }


        public void startObserving() {
            final ContentResolver cr = mContext.getContentResolver();
            cr.unregisterContentObserver(this);
            cr.registerContentObserver(
                    BRIGHTNESS_MODE_URI,
                    false, this, UserHandle.USER_ALL);
            cr.registerContentObserver(
                    BRIGHTNESS_URI,
                    false, this, UserHandle.USER_ALL);
            cr.registerContentObserver(
                    BRIGHTNESS_ADJ_URI,
                    false, this, UserHandle.USER_ALL);
        }


        public void stopObserving() {
            final ContentResolver cr = mContext.getContentResolver();
            cr.unregisterContentObserver(this);
        }


    }


    public BrightnessController(Context context, ImageView icon, ToggleSlider control) {
        mContext = context;
        mIcon = icon;
        mControl = control;
        mHandler = new Handler();
        mUserTracker = new CurrentUserTracker(mContext) {
            @Override
            public void onUserSwitched(int newUserId) {
                updateMode();
                updateSlider();
            }
        };
        mBrightnessObserver = new BrightnessObserver(mHandler);


        PowerManager pm = (PowerManager)context.getSystemService(Context.POWER_SERVICE);
        mMinimumBacklight = pm.getMinimumScreenBrightnessSetting();
        mMaximumBacklight = pm.getMaximumScreenBrightnessSetting();


Log.v("BrightnessController", "[webber]mMinimumBacklight=" + mMinimumBacklight);
        Log.v("BrightnessController", "[webber]mMaximumBacklight=" + mMaximumBacklight);


        PackageManager packageManager = context.getPackageManager();
        if (packageManager.hasSystemFeature(PackageManager.FEATURE_SENSOR_LIGHT)) {
                mAutomaticAvailable = context.getResources().getBoolean(
                        com.android.internal.R.bool.config_automatic_brightness_available);
        } else {
                mAutomaticAvailable = false;
                final CompoundButton toggle = (CompoundButton)control.findViewById(R.id.toggle);
                toggle.setClickable(false);
        }


        mPower = IPowerManager.Stub.asInterface(ServiceManager.getService("power"));
    }


    public void addStateChangedCallback(BrightnessStateChangeCallback cb) {
        mChangeCallbacks.add(cb);
    }


    public boolean removeStateChangedCallback(BrightnessStateChangeCallback cb) {
        return mChangeCallbacks.remove(cb);
    }


    @Override
    public void onInit(ToggleSlider control) {
        // Do nothing
    }


    public void registerCallbacks() {
        if (mListening) {
            return;
        }


        mBrightnessObserver.startObserving();
        mUserTracker.startTracking();


        // Update the slider and mode before attaching the listener so we don't
        // receive the onChanged notifications for the initial values.
        updateMode();
        updateSlider();


        mControl.setOnChangedListener(this);
        mListening = true;
    }


    /** Unregister all call backs, both to and from the controller */
    public void unregisterCallbacks() {
        if (!mListening) {
            return;
        }


        mBrightnessObserver.stopObserving();
        mUserTracker.stopTracking();
        mControl.setOnChangedListener(null);
        mListening = false;
    }


    @Override
    public void onChanged(ToggleSlider view, boolean tracking, boolean automatic, int value) {
        updateIcon(mAutomatic);
        if (mExternalChange) return;


Log.v("BrightnessController", "[webber5555]value=" + value);   


        if (!mAutomatic) {
            final int val = value + mMinimumBacklight;
//            setBrightness(val);
Log.v("BrightnessController", "[webber]val=" + val);   
            if (!tracking) {
                AsyncTask.execute(new Runnable() {
                        public void run() {
                            Settings.System.putIntForUser(mContext.getContentResolver(),
                                    Settings.System.SCREEN_BRIGHTNESS, val,
                                    UserHandle.USER_CURRENT);
                        }
                    });
            }
        } else {
            final float adj = value / (BRIGHTNESS_ADJ_RESOLUTION / 2f) - 1;
//            setBrightnessAdj(adj);
Log.v("BrightnessController", "[webber]adj=" + adj);   
            if (!tracking) {
                AsyncTask.execute(new Runnable() {
                    public void run() {
                        Settings.System.putFloatForUser(mContext.getContentResolver(),
                                Settings.System.SCREEN_AUTO_BRIGHTNESS_ADJ, adj,
                                UserHandle.USER_CURRENT);
                    }
                });
            }
        }


        for (BrightnessStateChangeCallback cb : mChangeCallbacks) {
            cb.onBrightnessLevelChanged();
        }
    }


    private void setMode(int mode) {
        Settings.System.putIntForUser(mContext.getContentResolver(),
                Settings.System.SCREEN_BRIGHTNESS_MODE, mode,
                mUserTracker.getCurrentUserId());
    }


    private void setBrightness(int brightness) {
        try {
            mPower.setTemporaryScreenBrightnessSettingOverride(brightness);
        } catch (RemoteException ex) {
        }
    }


    private void setBrightnessAdj(float adj) {
        try {
            mPower.setTemporaryScreenAutoBrightnessAdjustmentSettingOverride(adj);
        } catch (RemoteException ex) {
        }
    }


    private void updateIcon(boolean automatic) {
        if (mIcon != null) {
            mIcon.setImageResource(automatic && SHOW_AUTOMATIC_ICON ?
                    com.android.systemui.R.drawable.ic_qs_brightness_auto_on :
                    com.android.systemui.R.drawable.ic_qs_brightness_auto_off);
        }
    }


    /** Fetch the brightness mode from the system settings and update the icon */
    private void updateMode() {
        if (mAutomaticAvailable) {
            int automatic;
            automatic = Settings.System.getIntForUser(mContext.getContentResolver(),
                    Settings.System.SCREEN_BRIGHTNESS_MODE,
                    Settings.System.SCREEN_BRIGHTNESS_MODE_MANUAL,
                    UserHandle.USER_CURRENT);
            mAutomatic = automatic != Settings.System.SCREEN_BRIGHTNESS_MODE_MANUAL;
            updateIcon(mAutomatic);
        } else {
            mControl.setChecked(false);
            updateIcon(false /*automatic*/);
        }
    }


    /** Fetch the brightness from the system settings and update the slider */
    private void updateSlider() {
        if (mAutomatic) {
            float value = Settings.System.getFloatForUser(mContext.getContentResolver(),
                    Settings.System.SCREEN_AUTO_BRIGHTNESS_ADJ, 0,
                    UserHandle.USER_CURRENT);
            mControl.setMax((int) BRIGHTNESS_ADJ_RESOLUTION);
            mControl.setValue((int) ((value + 1) * BRIGHTNESS_ADJ_RESOLUTION / 2f));
        } else {
            int value;
            value = Settings.System.getIntForUser(mContext.getContentResolver(),
                    Settings.System.SCREEN_BRIGHTNESS, mMaximumBacklight,
                    UserHandle.USER_CURRENT);
            mControl.setMax(mMaximumBacklight - mMinimumBacklight);
            mControl.setValue(value - mMinimumBacklight);
        }
    }


}