framework之 ContextImpl文件解析

ContextImpl实现了context.java中的方法，
位于： base\core\java\android\content
关键方法：

static class ServiceFetcher {
        int mContextCacheIndex = -1;
        /**
         * Main entrypoint; only override if you don‘t need caching.
         */
        public Object getService(ContextImpl ctx) {
            ArrayList<Object> cache = ctx.mServiceCache;//mServiceCache是ArrayList<Object>类型对象 
            Object service;
            synchronized (cache) {
                if (cache.size() == 0) {
                    // Initialize the cache vector on first access.
                    // At this point sNextPerContextServiceCacheIndex
                    // is the number of potential services that are
                    // cached per-Context.
                    for (int i = 0; i < sNextPerContextServiceCacheIndex; i++) { // sNextPerContextServiceCacheIndex为每个Android服务的索引值 
                        cache.add(null);//添加null对象
                    }
                } else {// size不为0的时候，即，之前已经调用过getSystemService 
                    service = cache.get(mContextCacheIndex);
                    if (service != null) {
                        return service;
                    }
                }
                service = createService(ctx); // cache.size=0并且已经添加了一个null对象到cache里 
                cache.set(mContextCacheIndex, service); // 设置新创建的服务添加到cache里 
                return service;
            }
        }

      ctx.mServiceCache中没有元素，此时cache.size() = 0，为cache中添加null对象，再创建一个服务给这个个新创建的Activity，对于一个不是新的Activity来说，找到之前 cache中的索引，返回service

 /**
         * Override this to create a new per-Context instance of the
         * service.  getService() will handle locking and caching.
         */
        public Object createService(ContextImpl ctx) {
            throw new RuntimeException("Not implemented");
        }
    }
    /**
     * Override this class for services to be cached process-wide.
     */
    abstract static class StaticServiceFetcher extends ServiceFetcher {
        private Object mCachedInstance;


        @Override
        public final Object getService(ContextImpl unused) {
            synchronized (StaticServiceFetcher.this) {
                Object service = mCachedInstance;
                if (service != null) {
                    return service;
                }
                return mCachedInstance = createStaticService();
            }
        }


        public abstract Object createStaticService();
    }


    private static final HashMap<String, ServiceFetcher> SYSTEM_SERVICE_MAP =
            new HashMap<String, ServiceFetcher>();


    private static int sNextPerContextServiceCacheIndex = 0;
    private static void registerService(String serviceName, ServiceFetcher fetcher) {
        if (!(fetcher instanceof StaticServiceFetcher)) {
            fetcher.mContextCacheIndex = sNextPerContextServiceCacheIndex++;
        }
        SYSTEM_SERVICE_MAP.put(serviceName, fetcher);
    }

注册的服务有：

和ActivityManagerService高度粘合，窗口管理，这里最核心的就是输入事件的分发和管理。

40、USER_SERVICE

获取应用程序的信息，像包名、主线程的Looper、Theme、文件路径、contentResolver、SQLitedatabase

重写了Context.java中的接口，实现了Activity的启动关闭，Sendboardcast（消息的广播、接收）、Service的启动关闭、绑定，系统运行时的文件、权限的增加（grant）、检查（check）、删除（revoke）

framework之 ContextImpl文件解析,布布扣,bubuko.com

framework之 ContextImpl文件解析

原文：http://blog.csdn.net/ahjxly/article/details/20777963