Develop Reference

Two fragments and a button in Landscape mode in XML

I am a beginner at Android Studio.
What I am trying here is to make two fragments and the second fragment has a button.
I was wondering why this XML code below is not working..
I got this notification..
Rendering Problems: A <fragment> tag allows a layout file to dynamically include different layouts at runtime. At layout editing time the specific layout to be used is not known. You can choose which layout you would like previewed while editing the layout.
My questions..
Is it okay to add Button element inside Fragment?
Can I add Frame inside Fragment as well?
How can I solve this problem?
Thank you for your help!
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="horizontal"
android:layout_width="match_parent"
android:layout_height="match_parent">
<!--first fragment(left screen) -->
<fragment android:name="com.example.android.fragments.ArticleListFragment"
android:id="#+id/headlines_fragment"
android:layout_weight="1"
android:layout_width="0dp"
android:layout_height="match_parent" >
</fragment>
<!--second fragment(right screen) -->
<fragment android:name="com.example.android.fragments.ArticleFragment"
android:id="#+id/article_fragment"
android:layout_weight="2"
android:layout_width="0dp"
android:layout_height="match_parent">
<Button
android:orientation="vertical"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="#+id/article_new_fragment"
android:text="OK!" />
</fragment>
</LinearLayout>

You can add any view inside a fragment, just like you would do in an activity.
For what I can tell, that button is inside the activity layout.
So:
Go To com.example.android.fragments.ArticleFragment
Go to its method onCreateView (ctrl+F to look for it)
It should have a return statement, something like
inflater.inflate(R.layout.fragment_layout, container, false);
At this point, you should understand that this method returns the Fragment's layout.
Go to the layout specified in that line (in this case, it would be
R.layout.fragment_layout).
Put in that layout the button, run the app and you should see it.

Answering your questions:
Is it okay to add Button element inside Fragment?
Yes but in its own layout file. You define where is the layout file in you java fragment class.
Can I add Frame inside Fragment as well?
If you mean frameLayout, yes but also in the layout file of the fragment.

Use XML-design of a listview multiple times

I've written an app and now want to design the UI. The problem is that I have the same data (well, not the same, but the same kind of data since it's an XML readout) and now I wanted to design it. But I don't think I can get the design how I want it programmatically. So I thought I design it once with XML and then copy the layout in the for loop for the other data as well. Is this possible?
If yes, how is it possible? I finished now my XML for one entry and now I want that all the other entries have the same style and layout as the others... Thanks!

There is simple way to achieve this.
There is include tag in xml file which you can use one layout in multiple screen design.
for eg. you had create header for application so no need to use same code in all file, just you can include that portion in each xml file.
here is simple example which may help you.
Create a Re-usable Layout
titlebar.xml
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width=”match_parent”
android:layout_height="wrap_content"
android:background="#color/titlebar_bg">
<ImageView android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:src="#drawable/gafricalogo" />
</FrameLayout>
Use the Tag:
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width=”match_parent”
android:layout_height=”match_parent”
android:background="#color/app_bg"
android:gravity="center_horizontal">
<include layout="#layout/titlebar"/>
<TextView android:layout_width=”match_parent”
android:layout_height="wrap_content"
android:text="#string/hello"
android:padding="10dp" />
...
</LinearLayout>

You should be using an Adapter to define your ListView elements. In which case, you will define a layout for that adapter (using XML) that will apply to every element in your ListView.
Bottom line, use an Adapter, which will set the same XML layout for every element in your List.
(Check item #3)
http://docs.xamarin.com/guides/android/user_interface/working_with_listviews_and_adapters

Declaratively defining fragments inside ViewPager

I have 5 unique pages of xml that are fairly complex. I want to put the 5 pages inside a ViewPager. All of the samples I can find simply put identical contents in each page via code. I want to declaratively define the xml in the viewpager like the xml pasted below. But this does not work - the app stops with this xml.
If I can't declaratively define it, then can I load individual xml pages into the viewpager? I can find no examples that do this.
thanks,
Gary Blakely
<?xml version="1.0" encoding="utf-8"?>
<fragment >
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
<ImageView android:layout_width="match_parent"
android:layout_height="match_parent" android:id="#+id/imageView1"
android:src="#drawable/flashright" android:adjustViewBounds="true" android:scaleType="fitXY">
</ImageView>
</LinearLayout>
</fragment>
<fragment >
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
<ImageView android:layout_width="match_parent"
android:layout_height="match_parent" android:id="#+id/imageView1"
android:src="#drawable/flashleft" android:adjustViewBounds="true" android:scaleType="fitXY">
</ImageView>
</LinearLayout>
</fragment>

If I follow, you want to declare everything in XML and avoid any programmatic initialization from within your Activity containing the ViewPager. The only way I can think of doing this would be to define 3 different Fragment classes which reference 3 different xml layouts. You could then embed them in your above xml, replacing each <Fragment> element with <FragmentX> <FragmentY> <FragmentZ> etc. Personally, I would rather write 3 xml layouts and create a single Fragment implementation that takes a single int argument to designate which layout to load, and then do the small amount of programmatic initialization necessary to make such a solution work. The rationale being that there is less duplicated code.
EDIT:
Another approach that might more fully address your requirements is to replace your <Fragment> tags with <Layout> tags and give them id's. Then in your Activity code, store refs to them, remove them from the View in onCreate() and finally add each of the stored references into programmatically created instances of Fragment which you then add to your ViewPager. Very ugly but thats the only way I know of to declaratively define everything in XML. You'll still have the problem that its not clear from the XML that these elements are nested within a ViewPager so personally I don't see the point. ListView and ListFragment operate with the same kind of implicit association though so its not unprecedented.

Avoid to rewrite code for activities with the same layout

I'd like to run several Activities on my Application;I'd like each Activity to have a Linear Layout and to show an image as heading; basically I'd like every layout to start like this:
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:background="#color/Grey"
>
<ImageView android:id="#+id/imageHeader" android:src="#drawable/tf_header" android:layout_height="wrap_content" android:layout_width="fill_parent"
android:background="#color/Black" android:scaleType="fitXY"></ImageView>
Is it possible not to reapeat this code for each layout? Could I use themes or styles to avoid it? Thank you for your replies.

Yes thats possible use the <include> tag as described in Layout Tricks.
For your example I would add the image as <include> and have a LinearLayout in each Activity layout xml

One of my apps uses the same xml file for 30 or so classes, i just modify it in code to customize it. That approach may work, just leave every label in the xml blank and set it in the .class

Android - Switch between layouts

I have two layouts, what is the best way to switch between the two layouts when a user clicks on a button?

You could call setContentView(R.layout.layout2) on ButtonClick

The best way is to use android.widget.ViewFlipper. With it you can create different layout from xml and then switch among them with simple method like this:
ViewFlipper viewFlipper = (ViewFlipper) findViewById(R.id.myViewFlipper);
// you can switch between next and previous layout and display it
viewFlipper.showNext();
viewFlipper.showPrevious();
// or you can switch selecting the layout that you want to display
viewFlipper.setDisplayedChild(1);
viewFlipper.setDisplayedChild(viewFlipper.indexOfChild(findViewById(R.id.secondLayout)
Xml example with tree layouts:
<ViewFlipper
android:id="#+id/myViewFlipper"
android:layout_width="match_parent"
android:layout_height="match_parent" >
<LinearLayout
android:id="#+id/firstLayout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
[...]
</LinearLayout>
<LinearLayout
android:id="#+id/secondLayout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
[...]
</LinearLayout>
<LinearLayout
android:id="#+id/thirdLayout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
[...]
</LinearLayout>
</ViewFlipper>

Use ViewSwitcher.
make one layout file that includes two layouts. your two layouts should be place in viewswitcher.
associate an onclick listener that switch two layout with a button.
if you separate two layouts in different file, you can use tag in layout xml file.

Use "fragment manager" after creating fragments and putting your layouts into it on run time or "view pager" as it can also add swapping effect. Do not use setContentView(R.layout.your_layout) without clearing the previous layout (use "gone" or "clear") for changing layout on run time as it slows down your app (because now there are two layout running) and even creates confusion for the app.