SilentKnight SilentKnight - 4 months ago 9
Android Question

What is new features of Android Design Support Library and how to use its Snackbar?

Android M Preview for developers was released yesterday. As usual, many amazing new features are introduced. I noticed that

Snackbar
is one of them.

I have read the document about
Snackbar
, from which I learnt that Snackbar is in the library of Android Design Support Library, whose absolute path is
android.support.design.widget.Snackbar
.

And the document says that:


Snackbars provide lightweight feedback about an operation. They show
a brief message at the bottom of the screen on mobile and lower left
on larger devices. Snackbars appear above all other elements on
screen and only one can be displayed at a time.

They automatically disappear after a timeout or after user interaction
elsewhere on the screen, particularly after interactions that summon a
new surface or activity. Snackbars can be swiped off screen.


So, does
Snackbar
behave like a
Toast
or a
Dialog
? Can Snackbars be used in a layout file? How could I use it programmatically?

P.S.:


  • Any samples on use of Snackbar will be appreciated.

  • Android Design Support Library is a new support library, could
    somebody show me more details of this library?


Answer

As for Snackbar,it acts like a Toast but is different with a Toast. Snackbars are shown on the bottom of the screen and contain text with an optional single action. They automatically time out after the given time length by animating off the screen. In addition, users can swipe them away before the timeout which is considerably more powerful than toasts, another lightweight feedback mechanism.

You can use it programmatically like this:

Snackbar snackbar = Snackbar
  .make(parentLayout, R.string.snackbar_text, Snackbar.LENGTH_LONG)
  .setAction(R.string.snackbar_action, myOnClickListener);
snackbar.setActionTextColor(Color.CYAN);
View snackbarView = snackbar.getView();
snackbarView.setBackgroundColor(Color.YELLOW);//change Snackbar's background color;
TextView textView = (TextView)snackbarView .findViewById(android.support.design.R.id.snackbar_text);
textView.setTextColor(Color.BLUE);//change Snackbar's text color;
snackbar.show(); // Don’t forget to show!

Note the use of a View in the method of make() - Snackbar will attempt to find it ensure that it is anchored to its bottom.

What's more, Android Design Support Library is used for Android 2.1+ (API 7+), which features navigation drawer view, floating labels for editing text, floating action button, snackbar, tabs and something like that.

Navigation View

The navigation drawer can be an important focal point for identity and navigation within your app and consistency in the design here can make a considerable difference in how easy your app is to navigate, particularly for first time users. NavigationView makes this easier by providing the framework you need for the navigation drawer as well as the ability to inflate your navigation items through a menu resource.

You can use it like this:

<android.support.v4.widget.DrawerLayout
        xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:app="http://schemas.android.com/apk/res-auto"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:fitsSystemWindows="true">
    <!-- your content layout -->
    <android.support.design.widget.NavigationView
            android:layout_width="wrap_content"
            android:layout_height="match_parent"
            android:layout_gravity="start"
            app:headerLayout="@layout/drawer_header"
            app:menu="@menu/drawer"/>
</android.support.v4.widget.DrawerLayout>

As for the drawer menu, it could be:

<group android:checkableBehavior="single">
    <item
        android:id="@+id/navigation_item_1"
        android:checked="true"
        android:icon="@drawable/ic_android"
        android:title="@string/navigation_item_1"/>
    <item
        android:id="@+id/navigation_item_2"
        android:icon="@drawable/ic_android"
        android:title="@string/navigation_item_2"/>
</group>

or:

<item
    android:id="@+id/navigation_subheader"
    android:title="@string/navigation_subheader">
    <menu>
        <item
            android:id="@+id/navigation_sub_item_1"
            android:icon="@drawable/ic_android"
            android:title="@string/navigation_sub_item_1"/>
        <item
            android:id="@+id/navigation_sub_item_2"
            android:icon="@drawable/ic_android"
            android:title="@string/navigation_sub_item_2"/>
    </menu>
</item>

You’ll get callbacks on selected items by setting a OnNavigationItemSelectedListener using setNavigationItemSelectedListener(). This provides you with the MenuItem that was clicked, allowing you to handle selection events, changed the checked status, load new content, programmatically close the drawer, or any other actions you may want.

Floating labels for editing text

Even the humble EditText has room to improve in material design. While an EditText alone will hide the hint text after the first character is typed, you can now wrap it in a TextInputLayout, causing the hint text to become a floating label above the EditText, ensuring that users never lose context in what they are entering. In addition to showing hints, you can also display an error message below the EditText by calling setError().

Floating Action Button

A floating action button is a round button denoting a primary action on your interface. The Design library’s FloatingActionButton gives you a single consistent implementation, by default colored using the colorAccent from your theme.

As FloatingActionButton extends ImageView, you’ll use android:src or any of the methods such as setImageDrawable() to control the icon shown within the FloatingActionButton.

Tabs

top level navigation pattern is commonly used for organizing different groupings of content. The Design library’s TabLayout implements both fixed tabs, where the view’s width is divided equally between all of the tabs, as well as scrollable tabs, where the tabs are not a uniform size and can scroll horizontally.

Tabs can be added programmatically:

TabLayout tabLayout = ...;
tabLayout.addTab(tabLayout.newTab().setText("Tab 1"));

If you want to use ViewPager for horizontal paging between tabs, you can create tabs directly from your PagerAdapter’s getPageTitle() and then connect the two together using setupWithViewPager(). This ensures that tab selection events update the ViewPager and page changes update the selected tab.

CoordinatorLayout and the app bar

the Design library introduces CoordinatorLayout, a layout which provides an additional level of control over touch events between child views, something which many of the components in the Design library take advantage of. If you try using an AppBarLayout allows your Toolbar and other views (such as tabs provided by TabLayout) to react to scroll events in a sibling view marked with a ScrollingViewBehavior. Therefore you can create a layout such as:

<android.support.design.widget.CoordinatorLayout
        xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:app="http://schemas.android.com/apk/res-auto"
        android:layout_width="match_parent"
        android:layout_height="match_parent">

     <! -- Your Scrollable View -->
    <android.support.v7.widget.RecyclerView
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            app:layout_behavior="@string/appbar_scrolling_view_behavior" />

    <android.support.design.widget.AppBarLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content">
   <android.support.v7.widget.Toolbar
                  ...
                  app:layout_scrollFlags="scroll|enterAlways">

        <android.support.design.widget.TabLayout
                  ...
                  app:layout_scrollFlags="scroll|enterAlways">
     </android.support.design.widget.AppBarLayout>
</android.support.design.widget.CoordinatorLayout>

Now, as the user scrolls the RecyclerView, the AppBarLayout can respond to those events by using the children’s scroll flags to control how they enter (scroll on screen) and exit (scroll off screen).

The Design library, AppCompat, and all of the Android Support Library are important tools in providing the building blocks needed to build a modern, great looking Android app without building everything from scratch.