ContentObserver 學習

1、ContentObserver——內容觀察者

目的是觀察(捕捉)特定Uri引起的數據庫的變化，繼而做一些相應的處理，ContentObserver是一個抽象類

類圖：

 監聽URI變化

   private static final class Transport extends IContentObserver.Stub {
        private ContentObserver mContentObserver;

        public Transport(ContentObserver contentObserver) {
            mContentObserver = contentObserver;
        }

        @Override
        public void onChange(boolean selfChange, Uri uri, int userId) {
            ContentObserver contentObserver = mContentObserver;
            if (contentObserver != null) {
                contentObserver.dispatchChange(selfChange, uri, userId);
            }
        }

        public void releaseContentObserver() {
            mContentObserver = null;
        }
    }

dispatchChange處理：

   private void dispatchChange(boolean selfChange, Uri uri, int userId) {
        if (mHandler == null) {
            onChange(selfChange, uri, userId);
        } else {
            mHandler.post(new NotificationRunnable(selfChange, uri, userId));
        }
    }

 2、實際觀察者--子類（觀察Settings.Global.BLUETOOTH_DISABLED_PROFILES的變化）

public class ProfileObserver extends ContentObserver {
    private Context mContext;
    private AdapterService mService;
    private AdapterStateObserver mStateObserver;

    public ProfileObserver(Context context, AdapterService service, Handler handler) {
        super(handler);
        mContext = context;
        mService = service;
        mStateObserver = new AdapterStateObserver(this);
    }

    public void start() {

//註冊內容觀察者
        mContext.getContentResolver()
                .registerContentObserver(
                        Settings.Global.getUriFor(Settings.Global.BLUETOOTH_DISABLED_PROFILES),
                        false, this);
    }

    private void onBluetoothOff() {
        mContext.unregisterReceiver(mStateObserver);
        Config.init(mContext);
        mService.enable();
    }

   //取消註冊

public void stop() {
        mContext.getContentResolver().unregisterContentObserver(this);
    }

    @Override

//內容變化回調
    public void onChange(boolean selfChange) {
        if (mService.isEnabled()) {
            mContext.registerReceiver(mStateObserver,
                    new IntentFilter(BluetoothAdapter.ACTION_STATE_CHANGED));
            mService.disable();
        }
    }