Develop Reference

Can you measure the height of a view on an activity that's not been loaded yet?

I want to make an animation on click that a button slides down to the position of another button and at the same time I'm loading another activity. This other button is on the new activity. Picture it as if a button from one activity is replacing a button on another activity, so it has to slide down to where the new button is.
Can I measure this new button's position before the activity is loaded? So I can get the animation right for all screen sizes.

Activities are designed to be used as full-screen components, meaning that you understand that the other activity that pops in is going to take the full screen. If that is your goal, you can use shared element transitions with the activities to get the desired effect: https://developer.android.com/training/transitions/start-activity#start-transition
On the other hand, if you need both activities to stay on the screen, than you should rather to use fragments, as activities are not suited for that. For more info on that approach, see here: https://developer.android.com/guide/navigation/navigation-animate-transitions

Scrolling a ViewPager programmatically, by a small amount

I have the requirement for what is effectively two activities side by side, allowing the user to scroll from one to the other, and back. I've decided that ViewPager is probably the best way to handle this, but am open to suggestions.
When the activity loads, the left hand view is displayed. I want to indicate to the user that the other view exists, by just scrolling it a small amount to the left and back again (similar to the way it's now common to show that a sliding drawer menu exists).
I've tried a number of things but have yet failed to find a method where both the views scroll smoothly together. Another way of interpretting the requirement is saying I want to programmatically fake a user flicking the page briefly.

Try calling the method fakeDragBy(float)! According to the documentation you need to first call beginFakeDrag() to initiate it and then call endFakeDrag(). This will mantain the ViewPagers default snapping behavior, so once you've revealed the other screen is there you don't have to animate the transition back, simply call endFakeDrag and the ViewPager will correctly snap back to the last screen (As long as you haven't dragged it past the half-way mark).

android two activity in one screen

I want to implement one android activity that have a button inside of it. when this button is clicked , andother activity runs.
The second activity slides from left to right and get just 80% width of the screen , and the 20% remaining spaced should be filled by left side of first activity( first acitivity slides to right)
How can I implement it?
I think I should have two activity in one screen!

I think Android Does not support two activitis in single screen. insted of activities u can use fragments

Better you should use fragments .. Check here http://developer.android.com/training/basics/fragments/index.html

Navigate horizontally and hit a button to go another layout vertically

I've been trying to figure out how to go about doing this specific task, but I can't quite figure out.
So, I have a ViewPager setup with 2 layouts that work perfectly. In the landing Pager, I have a button. What I'd like to do is, hit that button and the page animate vertically (up) to another layout.
I got the similar movement with starting a new Activity, but the problem with that, is that the title bar gets animated as well. So it doesn't give this fluid motion to the layout above.
I tried several things, but came up short with a lot of crashes.
Then I was thinking of having the landing Pager be a ScrollView and stack both layouts on top of each other, and navigate to a specific id, but came to no avail.
Does what I'm saying making sense? How should I go about creating something like this?
So to summarize.
Land on a page where you can swipe to one additional page (left).
Be able to hit a Button (on landing page) and animate up (vertically) to another layout.
All of this while having a static title bar.
Thanks in advance.

Android - How to change Activities within a TabActivity?

I currently have a TabActivity which has 4 tabs, within one of the tab's I want to be able to move forward and back between 4 different Activities.
However if I try to start a new Activity now it removes the TabActivty and starts a whole new Activity with no tab bars.
I have read about using view groups but that this is not best practice and also about using a view flipper but this doesn't seem to let me switch between different Activities only change the views within the Activity. I can't implement back functionality for exa,ple.
Can anyone point me in the right direction as to what I should be looking for as a solution to this?
EDIT:
Some more information:
Within the TabActivity my first screen will be a ListView that contains 4 rows, then selecting one of these will in turn load another ListView with 2 rows again within the TabActivity and then the 3rd screen will just contain some text depending on which option the user chose again within the Tab Activity.
Is a ViewFlipper the best solution here? It seems to me that it will require a lot of coding within one Activity if I use the ViewFlipper?

I have done something similar. I used the ViewFlipper to achieve this. You can override onBackPressed in your Activity so you can deal with moving back through your views.
There's a couple of ways of doing this but a simple way would be to just increment a counter in your Activity as you move to the next views, then in your onBackPressed method if counter != 0 just show the previous view, if counter == 0 call super.onBackPressed.
You can see in my video showing what the result could look like (ignore the bug being shown in the video).