如何使我的Android Swipeable Card View更像IOS 7邮件应用程序（滑动以显示按钮）

Question

如何使SwipeableCardViews更像IOS 7邮件应用程序（滑动以显示按钮）

到目前为止，我已经创建了一个Android应用程序，允许用户向左或向右滑动Cardviews。每张卡都有2个按钮，我将在以后分配功能。

（如下图所示）：

我想要完成的是（但还不知道如何），而不是向左或向右滑动以完全移除卡片。

相反，我想要滑动手势，以显示隐藏在右或左卡下面的按钮。

IOS 7邮件应用程序已经执行此功能（下面的屏幕截图）我想在Android中使用Cardviews （不是ListViews）执行此操作。

我该怎样做呢？

到目前为止我的代码：

MainActivity.java

public class MainActivity extends ActionBarActivity {
    private RecyclerView mRecyclerView;
    private CardViewAdapter mAdapter;

    private ArrayList<String> mItems;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        mItems = new ArrayList<>(30);
        for (int i = 0; i < 30; i++) {
            mItems.add(String.format("Card number %2d", i));
        }

        OnItemTouchListener itemTouchListener = new OnItemTouchListener() {
            @Override
            public void onCardViewTap(View view, int position) {
                Toast.makeText(MainActivity.this, "Tapped " + mItems.get(position), Toast.LENGTH_SHORT).show();
            }

            @Override
            public void onButton1Click(View view, int position) {
                Toast.makeText(MainActivity.this, "Clicked Button1 in " + mItems.get(position), Toast.LENGTH_SHORT).show();
            }

            @Override
            public void onButton2Click(View view, int position) {
                Toast.makeText(MainActivity.this, "Clicked Button2 in " + mItems.get(position), Toast.LENGTH_SHORT).show();
            }
        };

        mAdapter = new CardViewAdapter(mItems, itemTouchListener);

        mRecyclerView = (RecyclerView) findViewById(R.id.recycler_view);

        mRecyclerView.setLayoutManager(new LinearLayoutManager(this));
        mRecyclerView.setAdapter(mAdapter);

        SwipeableRecyclerViewTouchListener swipeTouchListener =
                new SwipeableRecyclerViewTouchListener(mRecyclerView,
                        new SwipeableRecyclerViewTouchListener.SwipeListener() {
                            @Override
                            public boolean canSwipe(int position) {
                                return true;
                            }

                            @Override
                            public void onDismissedBySwipeLeft(RecyclerView recyclerView, int[] reverseSortedPositions) {
                                for (int position : reverseSortedPositions) {
                                    mItems.remove(position);
                                    mAdapter.notifyItemRemoved(position);
                                }
                                mAdapter.notifyDataSetChanged();
                            }

                            @Override
                            public void onDismissedBySwipeRight(RecyclerView recyclerView, int[] reverseSortedPositions) {
                                for (int position : reverseSortedPositions) {
                                    mItems.remove(position);
                                    mAdapter.notifyItemRemoved(position);
                                }
                                mAdapter.notifyDataSetChanged();
                            }
                        });

        mRecyclerView.addOnItemTouchListener(swipeTouchListener);
    }

    /**
     * Interface for the touch events in each item
     */
    public interface OnItemTouchListener {
        /**
         * Callback invoked when the user Taps one of the RecyclerView items
         *
         * @param view     the CardView touched
         * @param position the index of the item touched in the RecyclerView
         */
        public void onCardViewTap(View view, int position);

        /**
         * Callback invoked when the Button1 of an item is touched
         *
         * @param view     the Button touched
         * @param position the index of the item touched in the RecyclerView
         */
        public void onButton1Click(View view, int position);

        /**
         * Callback invoked when the Button2 of an item is touched
         *
         * @param view     the Button touched
         * @param position the index of the item touched in the RecyclerView
         */
        public void onButton2Click(View view, int position);
    }

    /**
     * A simple adapter that loads a CardView layout with one TextView and two Buttons, and
     * listens to clicks on the Buttons or on the CardView
     */
    public class CardViewAdapter extends RecyclerView.Adapter<CardViewAdapter.ViewHolder> {
        private List<String> cards;
        private OnItemTouchListener onItemTouchListener;

        public CardViewAdapter(List<String> cards, OnItemTouchListener onItemTouchListener) {
            this.cards = cards;
            this.onItemTouchListener = onItemTouchListener;
        }

        @Override
        public ViewHolder onCreateViewHolder(ViewGroup viewGroup, int i) {
            View v = LayoutInflater.from(viewGroup.getContext()).inflate(R.layout.card_view_layout, viewGroup, false);
            return new ViewHolder(v);
        }

        @Override
        public void onBindViewHolder(ViewHolder viewHolder, int i) {
            viewHolder.title.setText(cards.get(i));
        }

        @Override
        public int getItemCount() {
            return cards == null ? 0 : cards.size();
        }

        public class ViewHolder extends RecyclerView.ViewHolder {
            private TextView title;
            private Button button1;
            private Button button2;

            public ViewHolder(View itemView) {
                super(itemView);
                title = (TextView) itemView.findViewById(R.id.card_view_title);
                button1 = (Button) itemView.findViewById(R.id.card_view_button1);
                button2 = (Button) itemView.findViewById(R.id.card_view_button2);

                button1.setOnClickListener(new View.OnClickListener() {
                    @Override
                    public void onClick(View v) {
                        onItemTouchListener.onButton1Click(v, getPosition());
                    }
                });

                button2.setOnClickListener(new View.OnClickListener() {
                    @Override
                    public void onClick(View v) {
                        onItemTouchListener.onButton2Click(v, getPosition());
                    }
                });

                itemView.setOnClickListener(new View.OnClickListener() {
                    @Override
                    public void onClick(View v) {
                        onItemTouchListener.onCardViewTap(v, getPosition());
                    }
                });
            }
        }
    }
}

SwipeableRecyclerViewTouchListener.java

public class SwipeableRecyclerViewTouchListener implements RecyclerView.OnItemTouchListener {
    // Cached ViewConfiguration and system-wide constant values
    private int mSlop;
    private int mMinFlingVelocity;
    private int mMaxFlingVelocity;
    private long mAnimationTime;

    // Fixed properties
    private RecyclerView mRecyclerView;
    private SwipeListener mSwipeListener;
    private int mViewWidth = 1; // 1 and not 0 to prevent dividing by zero

    // Transient properties
    private List<PendingDismissData> mPendingDismisses = new ArrayList<>();
    private int mDismissAnimationRefCount = 0;
    private float mDownX;
    private float mDownY;
    private boolean mSwiping;
    private int mSwipingSlop;
    private VelocityTracker mVelocityTracker;
    private int mDownPosition;
    private View mDownView;
    private boolean mPaused;
    private float mFinalDelta;

    /**
     * Constructs a new swipe touch listener for the given {@link android.support.v7.widget.RecyclerView}
     *
     * @param recyclerView The recycler view whose items should be dismissable by swiping.
     * @param listener     The listener for the swipe events.
     */
    public SwipeableRecyclerViewTouchListener(RecyclerView recyclerView, SwipeListener listener) {
        ViewConfiguration vc = ViewConfiguration.get(recyclerView.getContext());
        mSlop = vc.getScaledTouchSlop();
        mMinFlingVelocity = vc.getScaledMinimumFlingVelocity() * 16;
        mMaxFlingVelocity = vc.getScaledMaximumFlingVelocity();
        mAnimationTime = recyclerView.getContext().getResources().getInteger(
                android.R.integer.config_shortAnimTime);
        mRecyclerView = recyclerView;
        mSwipeListener = listener;


        /**
         * This will ensure that this SwipeableRecyclerViewTouchListener is paused during list view scrolling.
         * If a scroll listener is already assigned, the caller should still pass scroll changes through
         * to this listener.
         */
        mRecyclerView.setOnScrollListener(new RecyclerView.OnScrollListener() {
            @Override
            public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
                setEnabled(newState != RecyclerView.SCROLL_STATE_DRAGGING);
            }

            @Override
            public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
            }
        });
    }

    /**
     * Enables or disables (pauses or resumes) watching for swipe-to-dismiss gestures.
     *
     * @param enabled Whether or not to watch for gestures.
     */
    public void setEnabled(boolean enabled) {
        mPaused = !enabled;
    }

    @Override
    public boolean onInterceptTouchEvent(RecyclerView rv, MotionEvent motionEvent) {
        return handleTouchEvent(motionEvent);
    }

    @Override
    public void onTouchEvent(RecyclerView rv, MotionEvent motionEvent) {
        handleTouchEvent(motionEvent);
    }

    private boolean handleTouchEvent(MotionEvent motionEvent) {
        if (mViewWidth < 2) {
            mViewWidth = mRecyclerView.getWidth();
        }

        switch (motionEvent.getActionMasked()) {
            case MotionEvent.ACTION_DOWN: {
                if (mPaused) {
                    break;
                }

                // Find the child view that was touched (perform a hit test)
                Rect rect = new Rect();
                int childCount = mRecyclerView.getChildCount();
                int[] listViewCoords = new int[2];
                mRecyclerView.getLocationOnScreen(listViewCoords);
                int x = (int) motionEvent.getRawX() - listViewCoords[0];
                int y = (int) motionEvent.getRawY() - listViewCoords[1];
                View child;
                for (int i = 0; i < childCount; i++) {
                    child = mRecyclerView.getChildAt(i);
                    child.getHitRect(rect);
                    if (rect.contains(x, y)) {
                        mDownView = child;
                        break;
                    }
                }

                if (mDownView != null) {
                    mDownX = motionEvent.getRawX();
                    mDownY = motionEvent.getRawY();
                    mDownPosition = mRecyclerView.getChildPosition(mDownView);
                    if (mSwipeListener.canSwipe(mDownPosition)) {
                        mVelocityTracker = VelocityTracker.obtain();
                        mVelocityTracker.addMovement(motionEvent);
                    } else {
                        mDownView = null;
                    }
                }
                break;
            }

            case MotionEvent.ACTION_CANCEL: {
                if (mVelocityTracker == null) {
                    break;
                }

                if (mDownView != null && mSwiping) {
                    // cancel
                    mDownView.animate()
                            .translationX(0)
                            .alpha(1)
                            .setDuration(mAnimationTime)
                            .setListener(null);
                }
                mVelocityTracker.recycle();
                mVelocityTracker = null;
                mDownX = 0;
                mDownY = 0;
                mDownView = null;
                mDownPosition = ListView.INVALID_POSITION;
                mSwiping = false;
                break;
            }

            case MotionEvent.ACTION_UP: {
                if (mVelocityTracker == null) {
                    break;
                }

                mFinalDelta = motionEvent.getRawX() - mDownX;
                mVelocityTracker.addMovement(motionEvent);
                mVelocityTracker.computeCurrentVelocity(1000);
                float velocityX = mVelocityTracker.getXVelocity();
                float absVelocityX = Math.abs(velocityX);
                float absVelocityY = Math.abs(mVelocityTracker.getYVelocity());
                boolean dismiss = false;
                boolean dismissRight = false;
                if (Math.abs(mFinalDelta) > mViewWidth / 2 && mSwiping) {
                    dismiss = true;
                    dismissRight = mFinalDelta > 0;
                } else if (mMinFlingVelocity <= absVelocityX && absVelocityX <= mMaxFlingVelocity
                        && absVelocityY < absVelocityX && mSwiping) {
                    // dismiss only if flinging in the same direction as dragging
                    dismiss = (velocityX < 0) == (mFinalDelta < 0);
                    dismissRight = mVelocityTracker.getXVelocity() > 0;
                }
                if (dismiss && mDownPosition != ListView.INVALID_POSITION) {
                    // dismiss
                    final View downView = mDownView; // mDownView gets null'd before animation ends
                    final int downPosition = mDownPosition;
                    ++mDismissAnimationRefCount;
                    mDownView.animate()
                            .translationX(dismissRight ? mViewWidth : -mViewWidth)
                            .alpha(0)
                            .setDuration(mAnimationTime)
                            .setListener(new AnimatorListenerAdapter() {
                                @Override
                                public void onAnimationEnd(Animator animation) {
                                    performDismiss(downView, downPosition);
                                }
                            });
                } else {
                    // cancel
                    mDownView.animate()
                            .translationX(0)
                            .alpha(1)
                            .setDuration(mAnimationTime)
                            .setListener(null);
                }
                mVelocityTracker.recycle();
                mVelocityTracker = null;
                mDownX = 0;
                mDownY = 0;
                mDownView = null;
                mDownPosition = ListView.INVALID_POSITION;
                mSwiping = false;
                break;
            }

            case MotionEvent.ACTION_MOVE: {
                if (mVelocityTracker == null || mPaused) {
                    break;
                }

                mVelocityTracker.addMovement(motionEvent);
                float deltaX = motionEvent.getRawX() - mDownX;
                float deltaY = motionEvent.getRawY() - mDownY;
                if (!mSwiping && Math.abs(deltaX) > mSlop && Math.abs(deltaY) < Math.abs(deltaX) / 2) {
                    mSwiping = true;
                    mSwipingSlop = (deltaX > 0 ? mSlop : -mSlop);
                }

                if (mSwiping) {
                    mDownView.setTranslationX(deltaX - mSwipingSlop);
                    mDownView.setAlpha(Math.max(0f, Math.min(1f,
                            1f - Math.abs(deltaX) / mViewWidth)));
                    return true;
                }
                break;
            }
        }

        return false;
    }

    private void performDismiss(final View dismissView, final int dismissPosition) {
        // Animate the dismissed list item to zero-height and fire the dismiss callback when
        // all dismissed list item animations have completed. This triggers layout on each animation
        // frame; in the future we may want to do something smarter and more performant.

        final ViewGroup.LayoutParams lp = dismissView.getLayoutParams();
        final int originalHeight = dismissView.getHeight();

        ValueAnimator animator = ValueAnimator.ofInt(originalHeight, 1).setDuration(mAnimationTime);

        animator.addListener(new AnimatorListenerAdapter() {
            @Override
            public void onAnimationEnd(Animator animation) {
                --mDismissAnimationRefCount;
                if (mDismissAnimationRefCount == 0) {
                    // No active animations, process all pending dismisses.
                    // Sort by descending position
                    Collections.sort(mPendingDismisses);

                    int[] dismissPositions = new int[mPendingDismisses.size()];
                    for (int i = mPendingDismisses.size() - 1; i >= 0; i--) {
                        dismissPositions[i] = mPendingDismisses.get(i).position;
                    }

                    if (mFinalDelta > 0) {
                        mSwipeListener.onDismissedBySwipeRight(mRecyclerView, dismissPositions);
                    } else {
                        mSwipeListener.onDismissedBySwipeLeft(mRecyclerView, dismissPositions);
                    }

                    // Reset mDownPosition to avoid MotionEvent.ACTION_UP trying to start a dismiss
                    // animation with a stale position
                    mDownPosition = ListView.INVALID_POSITION;

                    ViewGroup.LayoutParams lp;
                    for (PendingDismissData pendingDismiss : mPendingDismisses) {
                        // Reset view presentation
                        pendingDismiss.view.setAlpha(1f);
                        pendingDismiss.view.setTranslationX(0);
                        lp = pendingDismiss.view.getLayoutParams();
                        lp.height = originalHeight;
                        pendingDismiss.view.setLayoutParams(lp);
                    }

                    // Send a cancel event
                    long time = SystemClock.uptimeMillis();
                    MotionEvent cancelEvent = MotionEvent.obtain(time, time,
                            MotionEvent.ACTION_CANCEL, 0, 0, 0);
                    mRecyclerView.dispatchTouchEvent(cancelEvent);

                    mPendingDismisses.clear();
                }
            }
        });

        animator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
            @Override
            public void onAnimationUpdate(ValueAnimator valueAnimator) {
                lp.height = (Integer) valueAnimator.getAnimatedValue();
                dismissView.setLayoutParams(lp);
            }
        });

        mPendingDismisses.add(new PendingDismissData(dismissPosition, dismissView));
        animator.start();
    }

    /**
     * The callback interface used by {@link SwipeableRecyclerViewTouchListener} to inform its client
     * about a swipe of one or more list item positions.
     */
    public interface SwipeListener {
        /**
         * Called to determine whether the given position can be swiped.
         */
        boolean canSwipe(int position);

        /**
         * Called when the item has been dismissed by swiping to the left.
         *
         * @param recyclerView           The originating {@link android.support.v7.widget.RecyclerView}.
         * @param reverseSortedPositions An array of positions to dismiss, sorted in descending
         *                               order for convenience.
         */
        void onDismissedBySwipeLeft(RecyclerView recyclerView, int[] reverseSortedPositions);

        /**
         * Called when the item has been dismissed by swiping to the right.
         *
         * @param recyclerView           The originating {@link android.support.v7.widget.RecyclerView}.
         * @param reverseSortedPositions An array of positions to dismiss, sorted in descending
         *                               order for convenience.
         */
        void onDismissedBySwipeRight(RecyclerView recyclerView, int[] reverseSortedPositions);
    }

    class PendingDismissData implements Comparable<PendingDismissData> {
        public int position;
        public View view;

        public PendingDismissData(int position, View view) {
            this.position = position;
            this.view = view;
        }

        @Override
        public int compareTo(@NonNull PendingDismissData other) {
            // Sort by descending position
            return other.position - position;
        }
    }
}

activity_main.xml中

<android.support.v7.widget.RecyclerView xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/recycler_view"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:scrollbars="vertical">

</android.support.v7.widget.RecyclerView>

card_view_layout.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.v7.widget.CardView xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:card_view="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:layout_margin="5dp"
    android:clickable="true"
    android:foreground="?android:attr/selectableItemBackground"
    android:orientation="vertical"
    card_view:cardCornerRadius="5dp">

    <RelativeLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <TextView
            android:id="@+id/card_view_title"
            android:layout_width="match_parent"
            android:layout_height="50dp"
            android:layout_alignParentTop="true"
            android:layout_centerHorizontal="true"
            android:gravity="center"
            android:textColor="@android:color/black"
            android:textSize="24sp" />

        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_alignParentBottom="true"
            android:layout_below="@id/card_view_title"
            android:layout_centerHorizontal="true"
            android:gravity="center">

            <Button
                android:id="@+id/card_view_button1"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text="Button1" />

            <Button
                android:id="@+id/card_view_button2"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text="Button2" />
        </LinearLayout>
    </RelativeLayout>

</android.support.v7.widget.CardView>

Answer 1

仅供参考，您可以使用这些swipe layout库。它包括您正在搜索的滑动操作。希望它有所帮助

Answer 2

我刚刚做到了这一点。这就是它的样子：

我没有任何CardView，但您可以拥有任何布局（因此您可以添加支持库CardView或您喜欢的任何内容。）

这就是我做的。我用了this library。由于库有minSdkVersion 15而我们有14，我直接从GitHub复制粘贴以下类：OnItemClickListener，RecyclerViewAdapter，SwipeableItemClickListener，SwipeToDismissTouchListener和ViewAdapter（如果您使用RecyclerView，这是您唯一需要的。）

由于尚未更新lib，因此您需要将以下方法添加到SwipeableItemClickListener中：

@Override
    public void onRequestDisallowInterceptTouchEvent(boolean disallowIntercept) {
}

您的列表项布局应具有以下结构：

<FrameLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="@dimen/list_item_article_height"
    >

    <!-- This is the layout you see always -->    
    <include
        layout="@layout/list_item_article"
        tools:visibility="gone"
        />

    <!-- This is the layout shown after swiping. Must have visibility="gone" -->
    <LinearLayout
        android:visibility="gone"
        tools:visibility="visible"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="horizontal"
        >    
        <TextView
            android:id="@+id/swipe_cancel"
            android:layout_width="wrap_content"
            android:layout_height="match_parent"
            android:layout_weight="2"
            android:text="@string/swipe_cancel"
            android:gravity="center"
            />    
        <TextView
            android:id="@+id/swipe_delete"
            android:layout_width="wrap_content"
            android:layout_height="match_parent"
            android:layout_weight="1"
            android:text="@string/swipe_delete"
            android:gravity="center"
            android:background="#f00"
            android:textColor="#fff"
            />    
    </LinearLayout>    
</FrameLayout>

然后在创建Activity/Fragment并设置适配器后，只需将此代码添加到RecyclerView：

final SwipeToDismissTouchListener<RecyclerViewAdapter> touchListener =
        new SwipeToDismissTouchListener<>(
                new RecyclerViewAdapter(mRecyclerView),
                new SwipeToDismissTouchListener.DismissCallbacks<RecyclerViewAdapter>() {
                    @Override
                    public boolean canDismiss(int position) {
                        return true;
                    }
                    @Override
                    public void onDismiss(RecyclerViewAdapter recyclerView, int position) {
                        // remove item at position and notify adapter
                    }
                }
        );
mRecyclerView.setOnTouchListener(touchListener);
mRecyclerView.addOnScrollListener((RecyclerView.OnScrollListener) touchListener.makeScrollListener());
mRecyclerView.addOnItemTouchListener(new SwipeableItemClickListener(
        getActivity(),
        new OnItemClickListener() {
            @Override
            public void onItemClick(View view, int position) {
                if (view.getId() == R.id.swipe_delete) {
                    touchListener.processPendingDismisses();
                } else {
                    touchListener.undoPendingDismiss();
                }
            }
        }
));

Answer 3

如果您只想添加和删除按钮，可以使用RecyclerView但使用RecyclerView.Adapter而不是CardViewAdapter。 这是一个例子：

public class MyActivity extends Activity {
    private RecyclerView mRecyclerView;
    private RecyclerView.Adapter mAdapter;
    private RecyclerView.LayoutManager mLayoutManager;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.my_activity);
        mRecyclerView = (RecyclerView) findViewById(R.id.my_recycler_view);

        // use this setting to improve performance if you know that changes
        // in content do not change the layout size of the RecyclerView
        mRecyclerView.setHasFixedSize(true);

        // use a linear layout manager
        mLayoutManager = new LinearLayoutManager(this);
        mRecyclerView.setLayoutManager(mLayoutManager);

        // specify an adapter (see also next example)
        mAdapter = new MyAdapter(myDataset);
        mRecyclerView.setAdapter(mAdapter);
    }
    ...
}

public class MyAdapter extends RecyclerView.Adapter<MyAdapter.ViewHolder> {
    private String[] mDataset;

    // Provide a reference to the views for each data item
    // Complex data items may need more than one view per item, and
    // you provide access to all the views for a data item in a view holder
    public static class ViewHolder extends RecyclerView.ViewHolder {
        // each data item is just a string in this case
        public TextView mTextView;
        public ViewHolder(TextView v) {
            super(v);
            mTextView = v;
        }
    }

    // Provide a suitable constructor (depends on the kind of dataset)
    public MyAdapter(String[] myDataset) {
        mDataset = myDataset;
    }

    // Create new views (invoked by the layout manager)
    @Override
    public MyAdapter.ViewHolder onCreateViewHolder(ViewGroup parent,
                                                   int viewType) {
        // create a new view
        View v = LayoutInflater.from(parent.getContext())
                               .inflate(R.layout.my_text_view, parent, false);
        // set the view's size, margins, paddings and layout parameters
        ...
        ViewHolder vh = new ViewHolder(v);
        return vh;
    }

    // Replace the contents of a view (invoked by the layout manager)
    @Override
    public void onBindViewHolder(ViewHolder holder, int position) {
        // - get element from your dataset at this position
        // - replace the contents of the view with that element
        holder.mTextView.setText(mDataset[position]);

    }

    // Return the size of your dataset (invoked by the layout manager)
    @Override
    public int getItemCount() {
        return mDataset.length;
    }
}