将InitCommandBuffer独立，为支持resize需要重建cmd buffer做准备

example/Vulkan/VulkanAppFramework.h

@@ -82,6 +82,22 @@ public:
             return(false);
 
         shader_manage=device->CreateShaderModuleManage();
+        db=new SceneDB(device);
+
+        InitCommandBuffer();
+
+        return(true);
+    }
+
+    void InitCommandBuffer()
+    {
+        if(cmd_buf)
+        {
+            for(uint i=0;i<swap_chain_count;i++)
+                delete cmd_buf[i];
+
+            delete[] cmd_buf;
+        }
 
         swap_chain_count=device->GetSwapChainImageCount();
         {
@@ -90,10 +106,6 @@ public:
             for(uint i=0;i<swap_chain_count;i++)
                 cmd_buf[i]=device->CreateCommandBuffer();
         }
-
-        db=new SceneDB(device);
-
-        return(true);
     }
 
     void BuildCommandBuffer(vulkan::Pipeline *p,vulkan::DescriptorSets *ds,vulkan::Renderable *r)