定義檢視的 Elevation

檢視可以投射陰影， elevation 值決定了陰影的大小和順序。要設定 elevation 值，請使用  android:elevation  屬性：

<TextView
android:id="@+id/my_textview"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/next"
android:background="@color/white"
android:elevation="5dp" />

新的  translationZ  屬性使得你可以設計臨時變更 elevation 的動畫。elevation 變化在做觸控反饋時很有用。

建立列表和卡片

RecyclerView 是一個可插入性更強的 ListView，它支援不同的 layout 型別，並可以提升效能。CardView 使得你可以在卡片
內顯示一部分內容，並且和其他應用保持外觀一致。以下是一段樣例程式碼展示如何在 layout 中新增 CardView。

<android.support.v7.widget.CardView
android:id="@+id/card_view"
android:layout_width="200dp"
android:layout_height="200dp"
card_view:cardCornerRadius="3dp">
...
</android.support.v7.widget.CardView>
 

其中 card_view:cardCornerRadius 屬性是改變卡片的四個角的半徑的，如圓角，直角等。

下面通過官網的一個Sample來例項演示

效果圖

專案結構

程式碼

activity_card_view.xml:

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/container"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    android:paddingBottom="@dimen/activity_vertical_margin"
    tools:context="com.example.android.cardview.CardViewActivity"
    tools:ignore="MergeRootFrame" />
 

fragment_card_view:

<ScrollView
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:card_view="http://schemas.android.com/apk/res-auto"
    android:layout_height="match_parent"
    android:layout_width="match_parent"
    >

    <LinearLayout android:layout_width="match_parent"
                  android:layout_height="match_parent"
                  android:orientation="vertical"
                  android:paddingBottom="@dimen/activity_vertical_margin"
                  android:paddingTop="@dimen/activity_vertical_margin"
                  android:paddingLeft="@dimen/activity_horizontal_margin"
                  android:paddingRight="@dimen/activity_horizontal_margin"
        >
        <android.support.v7.widget.CardView
            android:id="@+id/cardview"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:elevation="100dp"
            card_view:cardBackgroundColor="@color/cardview_initial_background"
            card_view:cardCornerRadius="8dp"
            android:layout_marginLeft="@dimen/margin_large"
            android:layout_marginRight="@dimen/margin_large"
            >

            <TextView
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_margin="@dimen/margin_medium"
                android:text="@string/cardview_contents"
                />
        </android.support.v7.widget.CardView>

        <LinearLayout
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:layout_marginTop="@dimen/margin_large"
            android:orientation="horizontal"
            >
            <TextView
                android:layout_width="@dimen/seekbar_label_length"
                android:layout_height="wrap_content"
                android:layout_gravity="center_vertical"
                android:text="@string/cardview_radius_seekbar_text"
                />
            <SeekBar
                android:id="@+id/cardview_radius_seekbar"
                android:layout_width="fill_parent"
                android:layout_height="wrap_content"
                android:layout_margin="@dimen/margin_medium"
                />
        </LinearLayout>

        <LinearLayout
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:orientation="horizontal"
            >
            <TextView
                android:layout_width="@dimen/seekbar_label_length"
                android:layout_height="wrap_content"
                android:layout_gravity="center_vertical"
                android:text="@string/cardview_elevation_seekbar_text"
                />
            <SeekBar
                android:id="@+id/cardview_elevation_seekbar"
                android:layout_width="fill_parent"
                android:layout_height="wrap_content"
                android:layout_margin="@dimen/margin_medium"
                />
        </LinearLayout>
    </LinearLayout>
</ScrollView>

CardViewActivity:

public class CardViewActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_card_view);
        if (savedInstanceState == null) {
            getFragmentManager().beginTransaction()
                    .add(R.id.container, CardViewFragment.newInstance())
                    .commit();
        }
    }
}

CardViewFragment:

public class CardViewFragment extends Fragment {

    private static final String TAG = CardViewFragment.class.getSimpleName();

    /** The CardView widget. */
    //@VisibleForTesting
    CardView mCardView;

    /**
     * SeekBar that changes the cornerRadius attribute for the {@link #mCardView} widget.
     */
    //@VisibleForTesting
    SeekBar mRadiusSeekBar;

    /**
     * SeekBar that changes the Elevation attribute for the {@link #mCardView} widget.
     */
    //@VisibleForTesting
    SeekBar mElevationSeekBar;

    /**
     * Use this factory method to create a new instance of
     * this fragment using the provided parameters.
     *
     * @return A new instance of fragment NotificationFragment.
     */
    public static CardViewFragment newInstance() {
        CardViewFragment fragment = new CardViewFragment();
        fragment.setRetainInstance(true);
        return fragment;
    }

    public CardViewFragment() {
        // Required empty public constructor
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        return inflater.inflate(R.layout.fragment_card_view, container, false);
    }

    @Override
    public void onViewCreated(View view, Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);
        mCardView = (CardView) view.findViewById(R.id.cardview);
        mRadiusSeekBar = (SeekBar) view.findViewById(R.id.cardview_radius_seekbar);
        mRadiusSeekBar.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {
            @Override
            public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {
                Log.d(TAG, String.format("SeekBar Radius progress : %d", progress));
                mCardView.setRadius(progress);
            }
            @Override
            public void onStartTrackingTouch(SeekBar seekBar) {
                //Do nothing
            }

            @Override
            public void onStopTrackingTouch(SeekBar seekBar) {
                //Do nothing
            }
        });

        mElevationSeekBar = (SeekBar) view.findViewById(R.id.cardview_elevation_seekbar);
        mElevationSeekBar.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {
            @Override
            public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {
                Log.d(TAG, String.format("SeekBar Elevation progress : %d", progress));
                mCardView.setElevation(progress);
            }
            @Override
            public void onStartTrackingTouch(SeekBar seekBar) {
                //Do nothing
            }

            @Override
            public void onStopTrackingTouch(SeekBar seekBar) {
                //Do nothing
            }
        });
    }
}