这是使用ItemTouchHelper技术实现一个选择相册后,仿微信朋友圈图片拖拽更换位置,拖拽删除的一个功能.希望可以帮到大家.

完整项目地址:https://download.csdn.net/download/hzqit520/12342742

项目演示如下图:

主要的代码如下:

mItemTouchHelper = new ItemTouchHelper(new ItemTouchHelper.Callback() {
            @Override
            public boolean isLongPressDragEnabled () {
                return true;
            }

            @Override
            public void onSwiped (@NonNull RecyclerView.ViewHolder viewHolder, int direction) {
            }

            @Override
            public int getMovementFlags (@NonNull RecyclerView recyclerView, @NonNull RecyclerView.ViewHolder viewHolder) {
                int itemViewType = viewHolder.getItemViewType();
                if (itemViewType != GridImageAdapter.TYPE_CAMERA) {
                    viewHolder.itemView.setAlpha(0.7f);
                }
                return makeMovementFlags(ItemTouchHelper.DOWN | ItemTouchHelper.UP
                                                 | ItemTouchHelper.LEFT | ItemTouchHelper.RIGHT, 0);
            }

            @Override
            public boolean onMove (@NonNull RecyclerView recyclerView, @NonNull RecyclerView.ViewHolder viewHolder, @NonNull RecyclerView.ViewHolder target) {
                //得到item原来的position
                try {
                    int fromPosition = viewHolder.getAdapterPosition();
                    //得到目标position
                    int toPosition = target.getAdapterPosition();
                    int itemViewType = target.getItemViewType();
                    if (itemViewType != GridImageAdapter.TYPE_CAMERA) {
                        if (fromPosition < toPosition) {
                            for (int i = fromPosition; i < toPosition; i++) {
                                Collections.swap(mAdapter.getData(), i, i + 1);
                            }
                        } else {
                            for (int i = fromPosition; i > toPosition; i--) {
                                Collections.swap(mAdapter.getData(), i, i - 1);
                            }
                        }
                        mAdapter.notifyItemMoved(fromPosition, toPosition);
                    }
                } catch (Exception e) {
                    e.printStackTrace();
                }
                return true;
            }

            @Override
            public void onChildDraw (@NonNull Canvas c, @NonNull RecyclerView recyclerView,
                                     @NonNull RecyclerView.ViewHolder viewHolder, float dX, float dY, int actionState, boolean isCurrentlyActive) {
                int itemViewType = viewHolder.getItemViewType();
                if (itemViewType != GridImageAdapter.TYPE_CAMERA) {
                    if (null == mDragListener) {
                        return;
                    }
                    if (needScaleBig) {
                        //如果需要执行放大动画
                        viewHolder.itemView.animate().scaleXBy(0.1f).scaleYBy(0.1f).setDuration(100);
                        //执行完成放大动画,标记改掉
                        needScaleBig = false;
                        //默认不需要执行缩小动画，当执行完成放大 并且松手后才允许执行
                        needScaleSmall = false;
                    }
                    int sh = recyclerView.getHeight() + mTvDeleteText.getHeight();
                    int ry = mTvDeleteText.getTop() - sh;
                    if (dY >= ry) {
                        //拖到删除处
                        mDragListener.deleteState(true);
                        if (isUpward) {
                            //在删除处放手，则删除item
                            viewHolder.itemView.setVisibility(View.INVISIBLE);
                            mAdapter.delete(viewHolder.getAdapterPosition());
                            resetState();
                            return;
                        }
                    } else {//没有到删除处
                        if (View.INVISIBLE == viewHolder.itemView.getVisibility()) {
                            //如果viewHolder不可见，则表示用户放手，重置删除区域状态
                            mDragListener.dragState(false);
                        }
                        if (needScaleSmall) {//需要松手后才能执行
                            viewHolder.itemView.animate().scaleXBy(1f).scaleYBy(1f).setDuration(100);
                        }
                        mDragListener.deleteState(false);
                    }
                    super.onChildDraw(c, recyclerView, viewHolder, dX, dY, actionState, isCurrentlyActive);
                }
            }

            @Override
            public void onSelectedChanged (@Nullable RecyclerView.ViewHolder viewHolder, int actionState) {
                int itemViewType = viewHolder != null ? viewHolder.getItemViewType() : GridImageAdapter.TYPE_CAMERA;
                if (itemViewType != GridImageAdapter.TYPE_CAMERA) {
                    if (ItemTouchHelper.ACTION_STATE_DRAG == actionState && mDragListener != null) {
                        mDragListener.dragState(true);
                    }
                    super.onSelectedChanged(viewHolder, actionState);
                }
            }

            @Override
            public long getAnimationDuration (@NonNull RecyclerView recyclerView, int animationType, float animateDx, float animateDy) {
                needScaleSmall = true;
                isUpward = true;
                return super.getAnimationDuration(recyclerView, animationType, animateDx, animateDy);
            }

            @Override
            public void clearView (@NonNull RecyclerView recyclerView, @NonNull RecyclerView.ViewHolder viewHolder) {
                int itemViewType = viewHolder.getItemViewType();
                if (itemViewType != GridImageAdapter.TYPE_CAMERA) {
                    viewHolder.itemView.setAlpha(1.0f);
                    super.clearView(recyclerView, viewHolder);
                    mAdapter.notifyDataSetChanged();
                    resetState();
                }
            }
        });


        // 绑定拖拽事件
        mItemTouchHelper.attachToRecyclerView(mRecyclerView);

底部删除的文字和图片改变是根据拖拽监听,通过接口控制的,代码如下:

mDragListener = new DragListener() {
            @Override
            public void deleteState (boolean isDelete) {
                if (isDelete) {
                    mTvDeleteText.setText("松手即可删除");
                    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN_MR1) {
                        mTvDeleteText.setCompoundDrawablesRelativeWithIntrinsicBounds(0, R.mipmap.icon_let_go_delete, 0, 0);
                    }
                } else {
                    mTvDeleteText.setText("拖动到此处删除");
                    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN_MR1) {
                        mTvDeleteText.setCompoundDrawablesRelativeWithIntrinsicBounds(0, R.mipmap.picture_icon_delete, 0, 0);
                    }
                }
            }

            @Override
            public void dragState (boolean isStart) {
                int visibility = mTvDeleteText.getVisibility();
                if (isStart) {
                    if (visibility == View.GONE) {
                        mTvDeleteText.animate().alpha(1).setDuration(300).setInterpolator(new AccelerateInterpolator());
                        mTvDeleteText.setVisibility(View.VISIBLE);
                    }
                } else {
                    if (visibility == View.VISIBLE) {
                        mTvDeleteText.animate().alpha(0).setDuration(300).setInterpolator(new AccelerateInterpolator());
                        mTvDeleteText.setVisibility(View.GONE);
                    }
                }
            }
        };