Preheat the oven to 350 degrees. Drain the pineapple chunks, reserving ¼ cup of the juice.
Combine the flour, sugar, swiss cheese, reserved pineapple juice, pineapple chunks, and crushed pineapple in a large bowl. Pour the mixture into a 1 ½ quart casserole dish. Mix the cracker crumbs and butter in a small bowl, then sprinkle over the pineapple mixture.
Bake in the preheated oven until golden brown, about 30 minutes.