Android – Why use a CardView instead of a RelativeLayout or LinearLayout

androidandroid-cardviewandroid-layoutandroid-recyclerview

I have a RecyclerView for displaying a list of items. There is this android CardView class given by android to show card layout.
If I use a RelativeLayout and set its background to white it works the same way. Also in case of CardView I have to anyway add a childlayout to it which basically contains the all the views inside the card.
So I wanted to know if their is any benefit of using a CardView (which actually increases the hierarchy of the views) rather than a normal Layout directly.

Best Answer

There are some advantages of cards over layouts, including:

Rounded corners, elevation, etc - visual improvements that come "out of the box" by just using cards
They support various lengths of the content. Actually layouts support that too, but in the context of list/grid views they are meant to have the same size, whereas cards can vary in length (for example when you show comments or descriptions)
Cards on the same hierarchy level can have different types of content/views, unlike layouts (list/grid items) which should have similar layouts when you show a collection

All these and other features can be found in the card's design guideline.

In short:

I'd use cards when I want to display a collection of items which might have different lengths/heights depending on their content (like pictures with descriptions and comments) or a high number of supplemental actions.
I'd use Relative/Linear layouts when I want to display a simple collection of items, all/most of which have the same layout and a limited amount (max 1,2 lines) of text, an icon and an action,etc. elements that are the same for all items

Related Solutions

Android “Only the original thread that created a view hierarchy can touch its views.”

You have to move the portion of the background task that updates the UI onto the main thread. There is a simple piece of code for this:

runOnUiThread(new Runnable() {

    @Override
    public void run() {

        // Stuff that updates the UI

    }
});

Documentation for Activity.runOnUiThread.

Just nest this inside the method that is running in the background, and then copy paste the code that implements any updates in the middle of the block. Include only the smallest amount of code possible, otherwise you start to defeat the purpose of the background thread.

Android – Why fragments, and when to use fragments instead of activities

#1 & #2 what are the purposes of using a fragment & what are the advantages and disadvantages of using fragments compared to using activities/views/layouts?

Fragments are Android's solution to creating reusable user interfaces. You can achieve some of the same things using activities and layouts (for example by using includes). However; fragments are wired in to the Android API, from HoneyComb, and up. Let me elaborate;

The ActionBar. If you want tabs up there to navigate your app, you quickly see that ActionBar.TabListener interface gives you a FragmentTransaction as an input argument to the onTabSelected method. You could probably ignore this, and do something else and clever, but you'd be working against the API, not with it.
The FragmentManager handles «back» for you in a very clever way. Back does not mean back to the last activity, like for regular activities. It means back to the previous fragment state.
You can use the cool ViewPager with a FragmentPagerAdapter to create swipe interfaces. The FragmentPagerAdapter code is much cleaner than a regular adapter, and it controls instantiations of the individual fragments.
Your life will be a lot easier if you use Fragments when you try to create applications for both phones and tablets. Since the fragments are so tied in with the Honeycomb+ APIs, you will want to use them on phones as well to reuse code. That's where the compatibility library comes in handy.
You even could and should use fragments for apps meant for phones only. If you have portability in mind. I use ActionBarSherlock and the compatibility libraries to create "ICS looking" apps, that look the same all the way back to version 1.6. You get the latest features like the ActionBar, with tabs, overflow, split action bar, viewpager etc.

Bonus 2

The best way to communicate between fragments are intents. When you press something in a Fragment you would typically call StartActivity() with data on it. The intent is passed on to all fragments of the activity you launch.

Best Answer

Related Solutions

Android “Only the original thread that created a view hierarchy can touch its views.”

Android – Why fragments, and when to use fragments instead of activities

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