上一篇文章分析了回调注册监听的调用流程，对于数据的回调正好是注册监听的逆向调用。首先前面提到过在 HWC2On1Adapter 中就会直接转型为每一个回调到上层，这里我们就看一下屏幕热插拔回调（hotplugHook）的调用流程。

一、硬件回调

1、HWC2On1Adapter.cpp

源码位置：/hardware/interfaces/graphics/composer/2.1/utils/hwc2on1adapter/HWC2On1Adapter.cpp

class HWC2On1Adapter::Callbacks : public hwc_procs_t {
    public:
        explicit Callbacks(HWC2On1Adapter& adapter) : mAdapter(adapter) {
            invalidate = &invalidateHook;
            vsync = &vsyncHook;
            hotplug = &hotplugHook;
        }

        ……
        static void hotplugHook(const hwc_procs_t* procs, int display, int connected) {
            auto callbacks = static_cast<const Callbacks*>(procs);
            callbacks->mAdapter.hwc1Hotplug(display, connected);
        }

    private:
        HWC2On1Adapter& mAdapter;
};

        这是我们传入底层的 Callback，当屏幕出现热插