In a medium bowl, combine flour, baking powder, baking soda, and salt; set aside.
In a large mixing bowl beat the butter with an electric mixer on medium to high speed for 30 seconds. Add granulated sugar; beat until fluffy. Add eggs, beat until smooth.
Alternately add flour mixture and reserved pineapple juice to egg mixtgure, beating at low speed after each addition, just until combined. Fold in pinapple.
Spread batter in a greased 13x9x2 inch baking pan or dish. In a small bowl combine brown sugar, pecans, and coconut. Sprinkle over batter; bake in a 350 degree Fahrenheit oven about 35 minutes or until center is firm.