Android和設計模式：代理模式

 

    最近在繼續iPhone 業務的同時還須要從新拾起Android 。在有些生疏的狀況下，決定從Android 源碼中感悟一些Android 的風格和方式。在學習源碼的過程當中也發現了一些通用的模式，但願經過一個系列的文章總結和分享下。

    代理模式爲其餘對象提供一種代理以控制對這個對象的訪問。代理還分紅遠程代理、虛代理、保護代理和智能指針等。Android系統中利用AIDL定義一種遠程服務時就須要用到代理模式。以StatusBarManager爲例，其代理模式的類圖以下：

主要的實現代碼以下：

public class StatusBarManager {
    ......
    private Context mContext;
    private IStatusBarService mService;
    private IBinder mToken = new Binder();

    StatusBarManager(Context context) {
        mContext = context;
        mService = IStatusBarService.Stub.asInterface(
                ServiceManager.getService(Context.STATUS_BAR_SERVICE));
    }

    public void disable(int what) {
        try {
            mService.disable(what, mToken, mContext.getPackageName());
        } catch (RemoteException ex) {
            // system process is dead anyway.
            throw new RuntimeException(ex);
        }
    }
    public void expand() {
        try {
            mService.expand();
        } catch (RemoteException ex) {
            // system process is dead anyway.
            throw new RuntimeException(ex);
        }
    }
    public void collapse() {
        try {
            mService.collapse();
        } catch (RemoteException ex) {
            // system process is dead anyway.
            throw new RuntimeException(ex);
        }
    }

    public void setIcon(String slot, int iconId, int iconLevel) {
        try {
            mService.setIcon(slot, mContext.getPackageName(), iconId, iconLevel);
        } catch (RemoteException ex) {
            // system process is dead anyway.
            throw new RuntimeException(ex);
        }
    }

    public void removeIcon(String slot) {
        try {
            mService.removeIcon(slot);
        } catch (RemoteException ex) {
            // system process is dead anyway.
            throw new RuntimeException(ex);
        }
    }

    public void setIconVisibility(String slot, boolean visible) {         try {             mService.setIconVisibility(slot, visible);         } catch (RemoteException ex) {             // system process is dead anyway.             throw new RuntimeException(ex);         }     } }     其中做爲代理的StatusBarManager經過 IStatusBarService.Stub.asInterface(ServiceManager.getService(Context.STATUS_BAR_SERVICE))獲取到了遠程服務，用戶經過StatusBarManager同真正的服務交互。