官方文档 : https://developer.android.google.cn/reference/kotlin/androidx/recyclerview/widget/ItemTouchHelper

ItemTouchHelper 可以为 RecyclerView 添加 滑动删除效果 和 拖动效果 ;

ItemTouchHelper 需要与 RecyclerView 和 ItemTouchHelper.Callback 结合起来使用 ;

根据想要开发的功能 , 重写不同的方法 ;

如果是想要开发拖动效果相关的功能 , 重写 ItemTouchHelper.Callback 的 onMoved 方法 ;

如果想要开发滑动相关效果 , 重写 ItemTouchHelper.Callback 的 onSwiped 方法 ;

ItemTouchHelper 需要与 LayoutManager 布局管理器结合使用 ;

通过 继承 ItemTouchHelper.Callback 抽象类 , 或

实现 ItemTouchHelper.Callback 接口 ,

这两个操作 自定义 LayoutManager 布局管理器 , 可以达到最优化的效果 ;

看一下 Android 官方定义的 线性布局管理器 LinearLayoutManager , 就实现了 ItemTouchHelper.ViewDropHandler 接口 ;

默认情况下 , ItemTouchHelper 移动 item 组件的 translateX 或 translateY 属性 , 为其重新设置位置 ;

开发者可以自定义这些行为通过覆盖 ItemTouchHelper.Callback 的 onChildDraw 和 onChildDrawOver 方法 ;

大多数情况下只需要覆盖 onChildDraw 方法即可 ;

onChildDraw 方法原型 :

* If you would like to customize how your View's respond to user interactions, this is * a good place to override. *

* Default implementation translates the child by the given dX, * dY. * ItemTouchHelper also takes care of drawing the child after other children if it is being * dragged. This is done using child re-ordering mechanism. On platforms prior to L, this * is * achieved via {@link android.view.ViewGroup#getChildDrawingOrder(int, int)} and on L * and after, it changes View's elevation value to be greater than all other children.) * * @param c The canvas which RecyclerView is drawing its children * @param recyclerView The RecyclerView to which ItemTouchHelper is attached to * @param viewHolder The ViewHolder which is being interacted by the User or it was * interacted and simply animating to its original position * @param dX The amount of horizontal displacement caused by user's action * @param dY The amount of vertical displacement caused by user's action * @param actionState The type of interaction on the View. Is either {@link * #ACTION_STATE_DRAG} or {@link #ACTION_STATE_SWIPE}. * @param isCurrentlyActive True if this view is currently being controlled by the user or * false it is simply animating back to its original state. * @see #onChildDrawOver(Canvas, RecyclerView, ViewHolder, float, float, int, * boolean) */ public void onChildDraw(@NonNull Canvas c, @NonNull RecyclerView recyclerView, @NonNull ViewHolder viewHolder, float dX, float dY, int actionState, boolean isCurrentlyActive) { ItemTouchUIUtilImpl.INSTANCE.onDraw(c, recyclerView, viewHolder.itemView, dX, dY, actionState, isCurrentlyActive); } } }

onChildDrawOver 方法原型 :

* If you would like to customize how your View's respond to user interactions, this is * a good place to override. *

* Default implementation translates the child by the given dX, * dY. * ItemTouchHelper also takes care of drawing the child after other children if it is being * dragged. This is done using child re-ordering mechanism. On platforms prior to L, this * is * achieved via {@link android.view.ViewGroup#getChildDrawingOrder(int, int)} and on L * and after, it changes View's elevation value to be greater than all other children.) * * @param c The canvas which RecyclerView is drawing its children * @param recyclerView The RecyclerView to which ItemTouchHelper is attached to * @param viewHolder The ViewHolder which is being interacted by the User or it was * interacted and simply animating to its original position * @param dX The amount of horizontal displacement caused by user's action * @param dY The amount of vertical displacement caused by user's action * @param actionState The type of interaction on the View. Is either {@link * #ACTION_STATE_DRAG} or {@link #ACTION_STATE_SWIPE}. * @param isCurrentlyActive True if this view is currently being controlled by the user or * false it is simply animating back to its original state. * @see #onChildDrawOver(Canvas, RecyclerView, ViewHolder, float, float, int, * boolean) */ public void onChildDrawOver(@NonNull Canvas c, @NonNull RecyclerView recyclerView, ViewHolder viewHolder, float dX, float dY, int actionState, boolean isCurrentlyActive) { ItemTouchUIUtilImpl.INSTANCE.onDrawOver(c, recyclerView, viewHolder.itemView, dX, dY, actionState, isCurrentlyActive); } } }二、RecyclerView 相关资料

官方文档 :

使用 RecyclerView 创建动态列表 : https://developer.android.google.cn/guide/topics/ui/layout/recyclerview

高级 RecyclerView 自定义 : https://developer.android.google.cn/guide/topics/ui/layout/recyclerview-custom

RecyclerView 官方文档 : https://developer.android.google.cn/reference/androidx/recyclerview/widget/RecyclerView

RecyclerView.Adapter 官方文档 : https://developer.android.google.cn/reference/androidx/recyclerview/widget/RecyclerView.Adapter

RecyclerView.ViewHolder 官方文档 : https://developer.android.google.cn/reference/androidx/recyclerview/widget/RecyclerView.ViewHolder

RecyclerView.ItemDecoration 官方文档 : https://developer.android.google.cn/reference/androidx/recyclerview/widget/RecyclerView.ItemDecoration

GridLayoutManager 官方文档 : https://developer.android.google.cn/reference/androidx/recyclerview/widget/GridLayoutManager

LinearLayoutManager 官方文档 : https://developer.android.google.cn/reference/androidx/recyclerview/widget/LinearLayoutManager

StaggeredGridLayoutManager 官方文档 : https://developer.android.google.cn/reference/androidx/recyclerview/widget/StaggeredGridLayoutManager

ItemTouchHelper 官方文档 : https://developer.android.google.cn/reference/kotlin/androidx/recyclerview/widget/ItemTouchHelper

ItemTouchHelper.Callback 官方文档 : https://developer.android.google.cn/reference/kotlin/androidx/recyclerview/widget/ItemTouchHelper.Callback

代码示例 :

GitHub 源码地址 : https://github.com/han1202012/001_RecyclerView

博客源码快照 : https://download.csdn.net/download/han1202012/14984775

( 使用 Android Studio 打开 )