This lesson teaches you to
- Add a List View
- Create a Layout Implementation for List Items
- Create a Layout Definition for Items
- Create an Adapter to Populate the List
- Associate the Adapter and Set a Click Listener
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Lists let users select an item from a set of choices easily on wearable devices. This lesson shows you how to create lists in your Android Wear apps.
The Wearable UI Library includes the WearableListView
class, which is a list
implementation optimized for wearable devices..
Note: The Notifications sample in the Android SDK
demonstrates how to use WearableListView
in your apps. This sample is located in
the android-sdk/samples/android-20/wearable/Notifications
directory.
To create a list in your Android Wear apps:
- Add a
WearableListView
element to your activity's layout definition. - Create a custom layout implementation for your list items.
- Use this implementation to create a layout definition file for your list items.
- Create an adapter to populate the list.
- Assign the adapter to the
WearableListView
element.
These steps are described in detail in the following sections.
Add a List View
The following layout adds a list view to an activity using a BoxInsetLayout
, so
the list is displayed properly on both round and square devices:
<android.support.wearable.view.BoxInsetLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:app="http://schemas.android.com/apk/res-auto" android:background="@drawable/robot_background" android:layout_height="match_parent" android:layout_width="match_parent"> <FrameLayout android:id="@+id/frame_layout" android:layout_height="match_parent" android:layout_width="match_parent" app:layout_box="left|bottom|right"> <android.support.wearable.view.WearableListView android:id="@+id/wearable_list" android:layout_height="match_parent" android:layout_width="match_parent"> </android.support.wearable.view.WearableListView> </FrameLayout> </android.support.wearable.view.BoxInsetLayout>
Create a Layout Implementation for List Items
In many cases, each list item consists of an icon and a description. The
Notifications sample from the Android SDK implements a custom layout that extends
LinearLayout
to incorporate these two elements inside each list item.
This layout also implements the methods in the WearableListView.Item
interface
to animate the item's icon and fade the text in response to events from
WearableListView
as the user scrolls through the list.
public class WearableListItemLayout extends LinearLayout implements WearableListView.Item { private final float mFadedTextAlpha; private final int mFadedCircleColor; private final int mChosenCircleColor; private ImageView mCircle; private float mScale; private TextView mName; public WearableListItemLayout(Context context) { this(context, null); } public WearableListItemLayout(Context context, AttributeSet attrs) { this(context, attrs, 0); } public WearableListItemLayout(Context context, AttributeSet attrs, int defStyle) { super(context, attrs, defStyle); mFadedTextAlpha = getResources() .getInteger(R.integer.action_text_faded_alpha) / 100f; mFadedCircleColor = getResources().getColor(R.color.grey); mChosenCircleColor = getResources().getColor(R.color.blue); } // Get references to the icon and text in the item layout definition @Override protected void onFinishInflate() { super.onFinishInflate(); // These are defined in the layout file for list items // (see next section) mCircle = (ImageView) findViewById(R.id.circle); mName = (TextView) findViewById(R.id.name); } // Provide scaling values for WearableListView animations @Override public float getProximityMinValue() { return 1f; } @Override public float getProximityMaxValue() { return 1.6f; } @Override public float getCurrentProximityValue() { return mScale; } // Scale the icon for WearableListView animations @Override public void setScalingAnimatorValue(float scale) { mScale = scale; mCircle.setScaleX(scale); mCircle.setScaleY(scale); } // Change color of the icon, remove fading from the text @Override public void onScaleUpStart() { mName.setAlpha(1f); ((GradientDrawable) mCircle.getDrawable()).setColor(mChosenCircleColor); } // Change the color of the icon, fade the text @Override public void onScaleDownStart() { ((GradientDrawable) mCircle.getDrawable()).setColor(mFadedCircleColor); mName.setAlpha(mFadedTextAlpha); } }
Create a Layout Definition for Items
After you implement a custom layout for list items, you provide a layout definition file that specifies the layout parameters of each of the components inside a list item. The following layout definition uses the custom layout implementation from the previous section and defines an icon and a text view whose IDs match those in the layout implementation class:
<com.example.android.support.wearable.notifications.WearableListItemLayout xmlns:android="http://schemas.android.com/apk/res/android" android:gravity="center_vertical" android:layout_width="match_parent" android:layout_height="80dp"> <ImageView android:id="@+id/circle" android:layout_height="20dp" android:layout_margin="16dp" android:layout_width="20dp" android:src="@drawable/wl_circle"/> <TextView android:id="@+id/name" android:gravity="center_vertical|left" android:layout_width="wrap_content" android:layout_marginRight="16dp" android:layout_height="match_parent" android:fontFamily="sans-serif-condensed-light" android:lineSpacingExtra="-4sp" android:textColor="@color/text_color" android:textSize="16sp"/> </com.example.android.support.wearable.notifications.WearableListItemLayout>
Create an Adapter to Populate the List
The adapter populates the WearableListView
with content. The following simple
adapter populates the list with elements based on an array of strings:
private static final class Adapter extends WearableListView.Adapter { private String[] mDataset; private final Context mContext; private final LayoutInflater mInflater; // Provide a suitable constructor (depends on the kind of dataset) public Adapter(Context context, String[] dataset) { mContext = context; mInflater = LayoutInflater.from(context); mDataset = dataset; } // Provide a reference to the type of views you're using public static class ItemViewHolder extends WearableListView.ViewHolder { private TextView textView; public ItemViewHolder(View itemView) { super(itemView); // find the text view within the custom item's layout textView = (TextView) itemView.findViewById(R.id.name); } } // Create new views for list items // (invoked by the WearableListView's layout manager) @Override public WearableListView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) { // Inflate our custom layout for list items return new ItemViewHolder(mInflater.inflate(R.layout.list_item, null)); } // Replace the contents of a list item // Instead of creating new views, the list tries to recycle existing ones // (invoked by the WearableListView's layout manager) @Override public void onBindViewHolder(WearableListView.ViewHolder holder, int position) { // retrieve the text view ItemViewHolder itemHolder = (ItemViewHolder) holder; TextView view = itemHolder.textView; // replace text contents view.setText(mDataset[position]); // replace list item's metadata holder.itemView.setTag(position); } // Return the size of your dataset // (invoked by the WearableListView's layout manager) @Override public int getItemCount() { return mDataset.length; } }
Associate the Adapter and Set a Click Listener
In your activity, obtain a reference to the WearableListView
element from
your layout, assign an instance of the adapter to populate the list, and set a click listener
to complete an action when the user selects a particular list item.
public class WearActivity extends Activity implements WearableListView.ClickListener { // Sample dataset for the list String[] elements = { "List Item 1", "List Item 2", ... }; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.my_list_activity); // Get the list component from the layout of the activity WearableListView listView = (WearableListView) findViewById(R.id.wearable_list); // Assign an adapter to the list listView.setAdapter(new Adapter(this, elements)); // Set a click listener listView.setClickListener(this); } // WearableListView click listener @Override public void onClick(WearableListView.ViewHolder v) { Integer tag = (Integer) v.itemView.getTag(); // use this data to complete some action ... } @Override public void onTopEmptyRegionClick() { } }