android之RecycleView之ItemTouchHelper 处理拖拽、滑动删除

与RecycleView和ItemTouchHelper.Callback一起使用

ItemTouchHelper内部包含内部类ItemTouchHelper.Callback

public class ItemTouchHelper extends RecyclerView.ItemDecoration        implements RecyclerView.OnChildAttachStateChangeListener {

public abstract static class Callback {

/** @param viewHolder   正在被拖拽的viewHolder.* @param target       被正在拖拽的覆盖的viewHolder*                     dragged.*/

public abstract boolean onMove(RecyclerView recyclerView,ViewHolder viewHolder, ViewHolder target);

/**direction  滑动的方向*                   {@link #UP}, {@link #DOWN},*                   {@link #LEFT} or {@link #RIGHT}*/

public abstract void onSwiped(ViewHolder viewHolder, int direction);

/**makeFlag(ACTION_STATE_IDLE, RIGHT) | makeFlag(ACTION_STATE_SWIPE, LEFT | RIGHT);*/

public abstract int getMovementFlags(RecyclerView recyclerView,ViewHolder viewHolder);

/**被RecyclerView's onDraw调用*/

public void onChildDraw(Canvas c, RecyclerView recyclerView,        ViewHolder viewHolder,        float dX, float dY, int actionState, boolean isCurrentlyActive) {    sUICallback.onDraw(c, recyclerView, viewHolder.itemView, dX, dY, actionState,            isCurrentlyActive);}

/**被RecyclerView's onDraw调用，比较少用到*/

public void onChildDrawOver(Canvas c, RecyclerView recyclerView,        ViewHolder viewHolder,        float dX, float dY, int actionState, boolean isCurrentlyActive) {    sUICallback.onDrawOver(c, recyclerView, viewHolder.itemView, dX, dY, actionState,            isCurrentlyActive);}

public boolean isLongPressDragEnabled() {    return true;}

public boolean isItemViewSwipeEnabled() {    return true;}

/**当拖拽或者滑动改变的时候调用，复写是需调用父类方法*/

public void onSelectedChanged(ViewHolder viewHolder, int actionState) {    if (viewHolder != null) {        sUICallback.onSelected(viewHolder.itemView);    }}

……

/**默认Item长按时触发拖拽功能*/

public void startDrag(ViewHolder viewHolder) {    if (!mCallback.hasDragFlag(mRecyclerView, viewHolder)) {        Log.e(TAG, "Start drag has been called but swiping is not enabled");        return;    }    if (viewHolder.itemView.getParent() != mRecyclerView) {        Log.e(TAG, "Start drag has been called with a view holder which is not a child of "                + "the RecyclerView which is controlled by this ItemTouchHelper.");        return;    }    obtainVelocityTracker();    mDx = mDy = 0f;    select(viewHolder, ACTION_STATE_DRAG);}

public static interface ViewDropHandler {……}

使用：继承ItemTouchHelper.Callback

public class SimpleItemTouchHelperCallback extends ItemTouchHelper.Callback {    public static final float ALPHA_FULL = 1.0f;    private final ItemTouchHelperAdapter mAdapter;    public SimpleItemTouchHelperCallback(ItemTouchHelperAdapter adapter) {        mAdapter = adapter;    }    @Override    public boolean isLongPressDragEnabled() {        return true;    }    @Override    public boolean isItemViewSwipeEnabled() {        return true;    }    @Override    public int getMovementFlags(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder) {        if (recyclerView.getLayoutManager() instanceof GridLayoutManager) {            final int dragFlags = ItemTouchHelper.UP | ItemTouchHelper.DOWN | ItemTouchHelper.LEFT | ItemTouchHelper.RIGHT;            final int swipeFlags = 0;            return makeMovementFlags(dragFlags, swipeFlags);        } else {            final int dragFlags = ItemTouchHelper.UP | ItemTouchHelper.DOWN;            final int swipeFlags = ItemTouchHelper.START | ItemTouchHelper.END;            return makeMovementFlags(dragFlags, swipeFlags);        }    }    @Override    public boolean onMove(RecyclerView recyclerView, RecyclerView.ViewHolder source, RecyclerView.ViewHolder target) {        if (source.getItemViewType() != target.getItemViewType()) {            return false;        }        // Notify the adapter of the move        mAdapter.onItemMove(source.getAdapterPosition(), target.getAdapterPosition());        return true;    }    @Override    public void onSwiped(RecyclerView.ViewHolder viewHolder, int i) {        // Notify the adapter of the dismissal        mAdapter.onItemDismiss(viewHolder.getAdapterPosition());    }    @Override    public void onChildDraw(Canvas c, RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder, float dX, float dY, int actionState, boolean isCurrentlyActive) {        if (actionState == ItemTouchHelper.ACTION_STATE_SWIPE) {            // Fade out the view as it is swiped out of the parent's bounds            final float alpha = ALPHA_FULL - Math.abs(dX) / (float) viewHolder.itemView.getWidth();            viewHolder.itemView.setAlpha(alpha);            viewHolder.itemView.setTranslationX(dX);        } else {            super.onChildDraw(c, recyclerView, viewHolder, dX, dY, actionState, isCurrentlyActive);        }    }    @Override    public void onSelectedChanged(RecyclerView.ViewHolder viewHolder, int actionState) {        // We only want the active item to change        if (actionState != ItemTouchHelper.ACTION_STATE_IDLE) {            if (viewHolder instanceof ItemTouchHelperViewHolder) {                // Let the view holder know that this item is being moved or dragged                ItemTouchHelperViewHolder itemViewHolder = (ItemTouchHelperViewHolder) viewHolder;                itemViewHolder.onItemSelected();            }        }        super.onSelectedChanged(viewHolder, actionState);    }    @Override    public void clearView(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder) {        super.clearView(recyclerView, viewHolder);        viewHolder.itemView.setAlpha(ALPHA_FULL);        if (viewHolder instanceof ItemTouchHelperViewHolder) {            ItemTouchHelperViewHolder itemViewHolder = (ItemTouchHelperViewHolder) viewHolder;            itemViewHolder.onItemClear();        }    }}

android之RecycleView之ItemTouchHelper 处理拖拽、滑动删除

android之RecycleView之ItemTouchHelper 处理拖拽、滑动删除

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