I modelled a character but in the uv editor only the gun in the holster seems not the other objects.I dont know whats the problem.
The problem is that you are working in Local viewport.
You can swith from Local viewport to standard viewport and viceversa by pressing "/" key (on the numpad, or Shift+7). This will affect also the UV/Image editor (you can see the UVs only for the objects you see in local viewport).
The local viewport mode is useful because you can see only the selected objects, but you don't have to hide the other objects in the scene. Just select your object(s), press "/" and you see only them. Press "/" again and you will see all objects in the scene.
It seems very strange, that the "visible layers" panel is not on your screenshot. It should be directly right of the Global dropdown at the bottom right of your screen.
Unless you did hide the rest of the model by pressing H (undo via alt+H), you might have different parts of your model placed on different layers. You can make all those layers visible by using the visible layer panel or pressing 1,2,3,4,5,6,... on your keyboard to switch between those layers.