前言
RecyclerView依靠ItemTouchHelper，实现item的拖动与滑动功能。
使用ItemTouchHelper实现上下拖动的例子
首先我们需要继承重写 ItemTouchHelper.Callback
public class QuickReplyItemTouchCallback extends ItemTouchHelper.Callback {
private QuickReplyAdapter mAdapter;
private boolean mIsLongPressDragEnabled = true;
public QuickReplyItemTouchCallback(QuickReplyAdapter adapter) { //传入适配器
mAdapter = adapter;
}
public void setLongPressDragEnabled(boolean isLongPressDragEnabled) {
mIsLongPressDragEnabled = isLongPressDragEnabled;
}
@Override
public boolean isItemViewSwipeEnabled() { //是否启用左右滑动
return false;
}
@Override
public boolean isLongPressDragEnabled() { //返回设置是否长按拖动Item上下移动
return mIsLongPressDragEnabled;
}
@Override
public int getMovementFlags(@NonNull RecyclerView recyclerView, @NonNull RecyclerView.ViewHolder viewHolder) {
//在这个回调方法里我们返回我们需要的使用的动作功能
int dragFlags = ItemTouchHelper.UP | ItemTouchHelper.DOWN; //拖动 这里设置的UP 与 DOWN 表示允许上下拖动
int swipeFlags = ItemTouchHelper.ACTION_STATE_IDLE; //滑动 这里设置的ACTION_STATE_IDLE 表示我们将滑动动作设置为空闲
return makeMovementFlags(dragFlags, swipeFlags);
}
@Override
public boolean onMove(@NonNull RecyclerView recyclerView, @NonNull RecyclerView.ViewHolder viewHolder, @NonNull RecyclerView.ViewHolder target) {
//用于上下移动Item的回调方法，在这个方法里我们要主动将Adapter里的数据互相替换位置
mAdapter.onItemMove(viewHolder.getAdapterPosition(), target.getAdapterPosition());
//返回 true表示我们已经将Adapter里的数据互相替换位置
return true;
}
@Override
public void onSwiped(@NonNull RecyclerView.ViewHolder viewHolder, int direction) {
//因为我们不需要处理滑动，所以此处不写逻辑
}
}
Adapter更换位置的实现
/**
* 提供给QuickReplyItemTouchCallback类使用的移动Item位置的方法
* @param fromPosition
* @param toPosition
*/
public void onItemMove(int fromPosition, int toPosition) {
Collections.swap(mList, fromPosition, toPosition);//更换我们数据List的位置
notifyItemMoved(fromPosition, toPosition); //更换Adapter Item的视图位置
if (mOnChangeDataPositionListener != null){
mOnChangeDataPositionListener.onChange(mList);
}
}
在Activity里给RecyclerView添加ItemTouchHelper.Callback
LinearLayoutManager linearLayoutManager = new LinearLayoutManager(getContext(), LinearLayoutManager.VERTICAL, false);
mQuickReplyRecyclerView.setLayoutManager(linearLayoutManager);
mQuickReplyAdapter = new QuickReplyAdapter();
mQuickReplyRecyclerView.setAdapter(mQuickReplyAdapter);
mCallback = new QuickReplyItemTouchCallback(mQuickReplyAdapter);
ItemTouchHelper itemTouchHelper = new ItemTouchHelper(mCallback);
itemTouchHelper.attachToRecyclerView(mQuickReplyRecyclerView);
使用ItemTouchHelper实现左右滑动的例子
下面的这个例子是改变需要出现的View的宽度
public class SwitchListItemTouchCallback extends ItemTouchHelper.Callback {
private int mWidth = 0;
@Override
public boolean isLongPressDragEnabled() {
return false;
}
@Override
public boolean isItemViewSwipeEnabled() {
return true;
}
@Override
public int getMovementFlags(@NonNull RecyclerView recyclerView, @NonNull RecyclerView.ViewHolder viewHolder) {
int dragFlags = ItemTouchHelper.ACTION_STATE_IDLE;
int swipeFlags = ItemTouchHelper.LEFT | ItemTouchHelper.RIGHT;
return makeMovementFlags(dragFlags, swipeFlags);
}
@Override
public boolean onMove(@NonNull RecyclerView recyclerView, @NonNull RecyclerView.ViewHolder viewHolder, @NonNull RecyclerView.ViewHolder target) {
return false;
}
@Override
public void onSwiped(@NonNull RecyclerView.ViewHolder viewHolder, int direction) {
}
@Override
public void onChildDraw(@NonNull Canvas c, @NonNull RecyclerView recyclerView, @NonNull RecyclerView.ViewHolder viewHolder, float dX, float dY, int actionState, boolean isCurrentlyActive) {
if (actionState == ItemTouchHelper.ACTION_STATE_SWIPE) { //判断活动状态为左右滑动
Context context = recyclerView.getContext();
if (mWidth == 0) {
mWidth = UnitConversionUtil.dip2px(context, 80); //Button显示后最大的宽度。这里用了一个dp转px工具类
}
if (dX == 0){ //有时候点击也会被触发成swipe,这里判断不发生偏移量就跳过
return;
}
boolean isLeft = dX < 0;
SwitchListAdapter.ViewHolder itemViewHolder = (SwitchListAdapter.ViewHolder) viewHolder;
ConstraintLayout.LayoutParams layoutParams = (ConstraintLayout.LayoutParams) itemViewHolder.mDeleteBtn.getLayoutParams();
if (isLeft) {
layoutParams.width = Math.min((int) Math.abs(dX), mWidth);
} else {
layoutParams.width = Math.max((int) (mWidth - dX), 0);
}
itemViewHolder.mDeleteBtn.setLayoutParams(layoutParams);
} else {
super.onChildDraw(c, recyclerView, viewHolder, dX, dY, actionState, isCurrentlyActive);
}
}
@Override
public void clearView(@NonNull RecyclerView recyclerView, @NonNull RecyclerView.ViewHolder viewHolder) {
// super.clearView(recyclerView, viewHolder);
}
}
滚动整个View来实现，这个效果的关键点是那个需要隐藏或者显示的View 需要在父类布局的外面
布局例子：
关键点 app:layout_constraintLeft_toRightOf="parent"
<ImageButton
android:id="@+id/delete_btn"
android:layout_width="80dp"
android:layout_height="0dp"
android:background="@color/color_text_yellow"
android:src="@drawable/ic_delete_2"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintLeft_toRightOf="parent"
app:layout_constraintHorizontal_bias="0.5"
app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>
代码
@Override
public void onChildDraw(@NonNull Canvas c, @NonNull RecyclerView recyclerView, @NonNull RecyclerView.ViewHolder viewHolder, float dX, float dY, int actionState, boolean isCurrentlyActive) {
if (actionState == ItemTouchHelper.ACTION_STATE_SWIPE) {
Context context = recyclerView.getContext();
if (mWidth == 0) {
mWidth = UnitConversionUtil.dip2px(context, 80);
}
if (dX == 0){ //有时候点击也会被触发成swipe,这里判断不发生偏移量就跳过
return;
}
boolean isLeft = dX < 0;
SwitchListAdapter.ViewHolder itemViewHolder = (SwitchListAdapter.ViewHolder) viewHolder;
if (isLeft) {
itemViewHolder.rootView.setScrollX(Math.min((int) Math.abs(dX), mWidth));
} else {
itemViewHolder.rootView.setScrollX(Math.max((int) (mWidth - dX), 0));
}
} else {
super.onChildDraw(c, recyclerView, viewHolder, dX, dY, actionState, isCurrentlyActive);
}
}
End