Develop Reference

Using on Activity in Android to draw multiple UI's

I would like to know if it is wise/possible to have one activity that displays multiple different UI elements dynamically in a single layout?
So I want to have a single activity that loads a blank layout and then from code I add various UI elements such as buttons, text views etc. Then when a button is pressed, for that layout to clear and then from code draw the next set of UI elements on that same layout and so on and so forth?
Or would it be better to have multiple xml layout files and just inflate them each time I want to use a different layout, so then not create them from code?
Hope that makes sense.
Thanks,
Wihan

You should look into Fragments.
Activities are not intended to do what you would like them to do.
Instead you use one Activity and add a Fragment(s). Those Fragments can then be dynamically switched via code.
Take a tour => http://developer.android.com/guide/components/fragments.html

Yes this is very much possible. But Android xml layouts give a very easy way to use and manage different views. You could add views to ViewGroup and clear the ViewGroup.
I would also suggest using Fragments . This could be dynamically added and replaced.

How to reset widget layout inside a view layout during device rotation?

Well, i am developing new features inside a product which means lots of limitations i just can't break.
There is one activity which monitor the rotation event but use one unified layout for both portrait and landscape. Now i need to add some animations for several widgets inside the view.
For example, animation A to expand a toolbar, while B to collapse it.
But when i do A in landscape mode, and then rotate to portrait mode, the widgets still keep the position after animation A instead of the original layout configured in the xml file.
So what i want is to reset the layout partially. How can i achieve it???
Thanks!

Finally, i found a solution. Well may be not the best, it still solve my problem.
Insert a parent layout inside the activity view, let's say and put nothing inside it.
During the run time, add the child view according to the screen orientation dynamically as following:
Put the codes inside the onConfigurationChanged().
LinearLayout ll = (LinearLayout)findViewById(R.id.linearlayoutId);
View viewPor/viewLand = getLayoutInfalter().Infalte(R.layout.Por/Land, null);
ll.addView(viewPor/viewLand);
You may need a object associated with the specific view for manipulating the widgets inside the view for the animations.

Is it OK to add multiple views to root view of an Activity?

It may sound foolish, but I actually can't find anything on it.
Is it ok to add multiple views to the root view of activity in Android?
So for example I could go like this:
setContentView(R.layout.main);
setContentView(gLView);
setContentView(otherView);
Or simply retrieve it as a view
FrameLayout layout = (FrameLayout)this.getWindow().getDecorView().findViewById(android.R.id.content);
layout.addView(view1);
layout.addView(view2);
layout.addView(view3);
layout.addView(view4);
It all seems to work on devices I test, but is it guaranteed to work on all of them?
Or should I artificially create single FrameLayout to add to root view and add everything to this FrameLayout?
More experiments:
1) if I don't use setContentView and print:
Log.d("Test", this.getWindow().getDecorView().findViewById(android.R.id.content).getClass().getName());
I get: android.widget.FrameLayout
2) If I set content view to for example GLSurfaceView and print the same Log.d
It also prints android.widget.FrameLayout
3) And if I dont' use setContentView at all, and simply do
FrameLayout layout = (FrameLayout)this.getWindow().getDecorView().findViewById(android.R.id.content);
layout.addView(myView);
It attaches the view
So I assume that android.R.id.content returns not what you set by setContentView but the parent of what you set, or the actual root view in activity (which turns out is FrameLayout?)
And I am able to add multiple children to it this way, but question is:
Am I allowed to do that?

Yes, it's perfectly fine to add multiple content Views at the root level. The content Views are simply added to a FrameLayout container, and it is best practice to simply use it for your layout if a FrameLayout is all you require for it, instead of adding an additional container layer.
If you are adding a new content View, then you should use the addContentView() method instead of setContentView(), which would cause the existing content to be replaced instead.
Also, it is possible to add multiple Views to the content container in XML layouts as well by using the <merge> tag, which would just replace the base FrameLayout.

Calling setContentView several times will simply replace whatever view you set before. So what you want to do is create a root view that contains the multiple views you want to add and set the root view to your Activity with setContentView. Your second example with the FrameLayout is a good approach.

Your approach is valid at some extent. but its nice practice to call the setcontentView() once in activity.
this is because it will be very easy to maintain the Activity life cycle and reduce the app crash due to layout leak.
I personally call the setcontentView() once. I define all the layout in single XML file. Afterwords I call setVisibility(View.VISIBLE) and setVisibility(View.INVISIBLE) or setVisibility(View.GONE) to show or hide any particular layout containing my certain views.
Edit
Also its very easy to adjust the layout in XML because you can use simple drag and drop and If you are using relativeLayout then it will be very easy to place any view any where. but in Java code its some how difficult to place the views on your desired position
Hope this helps :)

Graphical Layout shows first view of ViewFlipper, how to see others?

I am using Eclipse and a ViewFlipper. In Graphical Layout, I want to see the second, third, and forth layouts of my views - right now, I can only see the first view. Any suggestions?

If I'm understanding you correctly, you want to see each view in the 'Graphical layout' tool? The way I do this, is instead of having all the layout work done in one xml (where your viewflipper is) I make each view a new layout xml. And then have each view (xml file) included into the view flipper by using this....
<include
layout="#layout/layout_media"
android:id="#+id/flipper_media" />
Hope this helps.

just put each layout in relative layout or linear what ever you are working with then with each layout you will work with the first one in the order and etc.. then at the end put each layout in the order you want later

I had to subclass the ViewSwitcher class to display an indeterminate ProgressBar until data is ready to display in the second view. I used isInEditMode() to determine whether I was actually running the app or just previewing in AS.
You should be able to add a custom attribute to choose which child to display. This might look a bit overkill, but if you happen to already have to subclass your ViewSwitcher or ViewFlipper, i think it is not a big deal.
I will try to put an example later.

How to replace a view after I've inflated?

I have built my interface by using ViewStubs, which I inflate during onCreate.
But later in my app, I want to change the View completely, by loading different View into the same place. How do I achieve that?

Remove the old View via removeView(). Then inflate and add the replacement via addView().
Though if you're going to be bouncing back and forth a lot, consider using a FrameLayout or ViewFlipper or something to have both views loaded at once, only making one visible.