Android 系統設置中顯示設置之亮度調節篇 

　　在上一篇博客中，我們學習了顯示設置中休眠設置和屏保設置的基本內容。在這一篇中我們來學習設備亮度的調節，首先還是學習在DisplaySettings.xml增加了一個叫做BrightnessPreference的preference的選項用來控制亮度調節。

　　步驟1：當用戶點擊BrightnessPreference的時候，由BrightnessPreference做對應的處理（注：其實是發送了一個廣播）　　

public class BrightnessPreference extends Preference {

    public BrightnessPreference(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    @Override
    protected void onClick() {
        //發送了一個顯示亮度調節對話框的廣播
        Intent intent = new Intent(Intent.ACTION_SHOW_BRIGHTNESS_DIALOG);
        getContext().sendBroadcastAsUser(intent, UserHandle.CURRENT_OR_SELF);
    }
}

 

 　　步驟2：對廣播的注冊並處理，有一個SettingsUI的類繼承自SystemUI，該類負責監聽上面的廣播並進行處理，詳見：

public class SettingsUI extends SystemUI {
    private static final String TAG = "SettingsUI";
    private static final boolean DEBUG = false;
    private final Handler mHandler = new Handler();
    private BrightnessDialog mBrightnessDialog;
    private BroadcastReceiver mIntentReceiver = new BroadcastReceiver() {
        @Override
        public void onReceive(Context context, Intent intent) {
            String action = intent.getAction();
            if (action.equals(Intent.ACTION_SHOW_BRIGHTNESS_DIALOG)) {
                if (DEBUG) Log.d(TAG, "showing brightness dialog");
                if (mBrightnessDialog == null) {
                    mBrightnessDialog = new BrightnessDialog(mContext);
                    mBrightnessDialog.setOnDismissListener(new DialogInterface.OnDismissListener() {
                        @Override
                        public void onDismiss(DialogInterface dialog) {
                            mBrightnessDialog = null;}});
                }
                if (!mBrightnessDialog.isShowing()) {
                    //顯示亮度調節的dialog
                    mBrightnessDialog.show(); }
            } else {
                Log.w(TAG, "unknown intent: " + intent);}}};

    public void start() {
        //監聽ACTION_SHOW_BRIGHTNESS_DIALOG廣播
        IntentFilter filter = new IntentFilter();
        filter.addAction(Intent.ACTION_SHOW_BRIGHTNESS_DIALOG);
        mContext.registerReceiverAsUser(mIntentReceiver, UserHandle.ALL, filter, null, mHandler);
    }

 

 　　步驟3：上面是負責顯示亮度調節的對話框，具體的設置需要查看BrightnessDialog，詳見：

 

    /**
     * Create the brightness dialog and any resources that are used for the
     * entire lifetime of the dialog.
     */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        
        Window window = getWindow();
        window.setType(WindowManager.LayoutParams.TYPE_VOLUME_OVERLAY);
        window.getAttributes().privateFlags |=
                WindowManager.LayoutParams.PRIVATE_FLAG_SHOW_FOR_ALL_USERS;
        window.clearFlags(WindowManager.LayoutParams.FLAG_DIM_BEHIND);
        window.requestFeature(Window.FEATURE_NO_TITLE);
        //dialog顯示的內容quick_settings_brightness_dialog.xml
        setContentView(R.layout.quick_settings_brightness_dialog);
        setCanceledOnTouchOutside(true);
    }


    @Override
    protected void onStart() {
        super.onStart();
        //對亮度的調節主要是使用了BrightnessController類
        mBrightnessController = new BrightnessController(getContext(),
                (ImageView) findViewById(R.id.brightness_icon),
                (ToggleSlider) findViewById(R.id.brightness_slider));
        dismissBrightnessDialog(mBrightnessDialogLongTimeout);
        mBrightnessController.addStateChangedCallback(this);
    }

 

 　　步驟4： BrightnessController詳解：

　　　　我們這里主要還是學習下一些基本的內容，具體包括獲取設備最大的亮度和最低的亮度值、如果設置屏幕的亮度、當前的亮度值和亮度調節模式保存和獲取的位置。

• • • 獲取設備的最大和最低亮度值　　　　　　  

        //獲取PowerManager對象
        PowerManager pm = (PowerManager)context.getSystemService(Context.POWER_SERVICE);
        //鑾峰彇璁懼鐨勬渶澶т寒搴?
        mMinimumBacklight = pm.getMinimumScreenBrightnessSetting();
        //鑾峰彇璁懼鐨勬渶浣庝寒搴?
        mMaximumBacklight = pm.getMaximumScreenBrightnessSetting();

 

• • • 設置屏幕亮度

        //首先獲取IPowerManager對象
        mPower = IPowerManager.Stub.asInterface(ServiceManager.getService("power"));

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

 

• • • 亮度值和亮度模式的讀取和存儲

    //設置亮度的設置模式，mode=0表示為手動，mode=1表示自動調節
    private void setMode(int mode) {
        //存儲位置為Settings.system中
        Settings.System.putIntForUser(mContext.getContentResolver(),
                Settings.System.SCREEN_BRIGHTNESS_MODE, mode,
                mUserTracker.getCurrentUserId());
    }
//以下的代碼是負責取出設置模式的

int automatic;
try {
　　　　automatic = Settings.System.getIntForUser(mContext.getContentResolver(),
　　　　Settings.System.SCREEN_BRIGHTNESS_MODE,
　　　　UserHandle.USER_CURRENT);
} catch (SettingNotFoundException snfe) {
　　　　automatic = 0;
}

 

          //以下的代碼是將亮度值保存到Settings.system中 
　　　　　　 if (!tracking) {
                AsyncTask.execute(new Runnable() {
                        public void run() {
                            Settings.System.putIntForUser(mContext.getContentResolver(),
                                    Settings.System.SCREEN_BRIGHTNESS, val,
                                    UserHandle.USER_CURRENT);
                        }
                    });
            }

 

    /** Fetch the brightness from the system settings and update the slider */
    private void updateSlider() {
        int value;
        try {
            //從Settings.System中獲取亮度值
            value = Settings.System.getIntForUser(mContext.getContentResolver(),
                    Settings.System.SCREEN_BRIGHTNESS,
                    UserHandle.USER_CURRENT);
        } catch (SettingNotFoundException ex) {
            value = mMaximumBacklight;
        }
        mControl.setMax(mMaximumBacklight - mMinimumBacklight);
        mControl.setValue(value - mMinimumBacklight);
    }

 

 

　　雜談：

　　　　我們在BrightnessController中找到了一個內部類叫做BrightnessController，它繼承自ContentObserver。該過程使用了觀察者設計模式，主要是用來負責對ContentProvider中指定的URI進行監聽，如果該URI對應的數據發生了變化就可以及時得到監聽並處理。它的使用請參考：http://www.cnblogs.com/slider/archive/2012/02/14/2351702.html 。

　　　　BrightnessController主要是監聽了

        private final Uri BRIGHTNESS_MODE_URI =
                Settings.System.getUriFor(Settings.System.SCREEN_BRIGHTNESS_MODE);//亮度調節模式
        private final Uri BRIGHTNESS_URI =
                Settings.System.getUriFor(Settings.System.SCREEN_BRIGHTNESS);//亮度值

        //當監聽的uri發生變化時，回調onChange函數
        @Override
        public void onChange(boolean selfChange, Uri uri) {
            if (selfChange) return;
            if (BRIGHTNESS_MODE_URI.equals(uri)) {
                updateMode();//更新模式
            } else if (BRIGHTNESS_URI.equals(uri)) {
                updateSlider();//更新拖動條
            } else {
                updateMode();
                updateSlider();
            }
            for (BrightnessStateChangeCallback cb : mChangeCallbacks) {
                cb.onBrightnessLevelChanged();
            }
        }

 

　　以上就是對亮度調節的基本內容，希望大家能夠喜歡，您的支持是我不懈的動力，當然不喜勿噴，有錯請指正！