is an amazing online tool for wireframing that has support also for
Android. You can easily build rapid prototypes with it. It even allows
you to link the pages together and simulate the UI interactions.
While building you can easily jump into a simulation
It supports multiple display sizes so you can see how your layout looks on a tablet.
[Edit] And as if the web app wasn't enough they also have a mobile app
you can put to your Android device and click through the prototypes
Login to the Fluid UI and you'll see a QR code that will open the mockup
on your phone (my example would look better if I hadn't added the
Android controls to it).
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