Android Navigation This is the source code for a simple app which lets you navigate through a tree. Clicking on the items enables or disables the items below them. Only the leftmost items are working in this example. Clicking on Home toggles the tree appearing below it. This app requires permission to read files from the SD card ( to launch PDFs from the application using the inbuilt PDF readers). Use ImageButtons, Toggle Buttons and other elements to customise the UI. This app is not what the prototype I made looks like, nor is it what any app should look like. This can just be a starting point for you to get started quickly. I wrote this sample app as a quick prototype on a 10 inch tablet, so scaling has not been taken care of.