我正在尝试将一些 iOS 功能移植到 Android。
我打算创建一个表格，向左滑动会显示 2 个按钮：编辑和删除。
我一直在玩它，我知道我已经非常接近了。秘密实际上在于 OnChildDraw 方法。
我想绘制一个适合文本删除的矩形，然后在其旁边绘制编辑文本及其各自的背景颜色。单击时剩余的空白应将该行恢复到其初始位置。
我已经设法在用户向侧面滑动时绘制背景，但我不知道如何添加侦听器，并且一旦用户向侧面滑动，拖动功能就开始出现异常。
我正在开发 Xamarin，但纯 java 解决方案也被接受，因为我可以轻松地将它们移植到 c#。
public class SavedPlacesItemTouchHelper : ItemTouchHelper.SimpleCallback
{
private SavedPlacesRecyclerviewAdapter adapter;
private Paint paint = new Paint();
private Context context;
public SavedPlacesItemTouchHelper(Context context, SavedPlacesRecyclerviewAdapter adapter) : base(ItemTouchHelper.ActionStateIdle, ItemTouchHelper.Left)
{
this.context = context;
this.adapter = adapter;
}
public override bool OnMove(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder, RecyclerView.ViewHolder target)
{
return false;
}
public override void OnSwiped(RecyclerView.ViewHolder viewHolder, int direction)
{
}
public override void OnChildDraw(Canvas c, RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder, float dX, float dY, int actionState, bool isCurrentlyActive)
{
float translationX = dX;
View itemView = viewHolder.ItemView;
float height = (float)itemView.Bottom - (float)itemView.Top;
if (actionState == ItemTouchHelper.ActionStateSwipe && dX <= 0) // Swiping Left
{
translationX = -Math.Min(-dX, height * 2);
paint.Color = Color.Red;
RectF background = new RectF((float)itemView.Right + translationX, (float)itemView.Top, (float)itemView.Right, (float)itemView.Bottom);
c.DrawRect(background, paint);
//viewHolder.ItemView.TranslationX = translationX;
}
else if (actionState == ItemTouchHelper.ActionStateSwipe && dX > 0) // Swiping Right
{
translationX = Math.Min(dX, height * 2);
paint.Color = Color.Red;
RectF background = new RectF((float)itemView.Right + translationX, (float)itemView.Top, (float)itemView.Right, (float)itemView.Bottom);
c.DrawRect(background, paint);
}
base.OnChildDraw(c, recyclerView, viewHolder, translationX, dY, actionState, isCurrentlyActive);
}
}
}
这就是我目前所拥有的。
如果您知道如何添加听众或有任何建议，请发表评论！
UPDATE:
我刚刚意识到，双击该行的白色剩余空间已经将该行恢复到其初始状态。虽然没有点击一下:(
我也遇到了同样的问题，并尝试在网上寻找解决方案。大多数解决方案都使用两层方法（一层视图项，另一层按钮），但我只想坚持使用 ItemTouchHelper。最后，我想出了一个可行的解决方案。请检查下面。
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Point;
import android.graphics.Rect;
import android.graphics.RectF;
import android.support.v7.widget.RecyclerView;
import android.support.v7.widget.helper.ItemTouchHelper;
import android.util.Log;
import android.view.GestureDetector;
import android.view.MotionEvent;
import android.view.View;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.Queue;
public abstract class SwipeHelper extends ItemTouchHelper.SimpleCallback {
public static final int BUTTON_WIDTH = YOUR_WIDTH_IN_PIXEL_PER_BUTTON
private RecyclerView recyclerView;
private List<UnderlayButton> buttons;
private GestureDetector gestureDetector;
private int swipedPos = -1;
private float swipeThreshold = 0.5f;
private Map<Integer, List<UnderlayButton>> buttonsBuffer;
private Queue<Integer> recoverQueue;
private GestureDetector.SimpleOnGestureListener gestureListener = new GestureDetector.SimpleOnGestureListener(){
@Override
public boolean onSingleTapConfirmed(MotionEvent e) {
for (UnderlayButton button : buttons){
if(button.onClick(e.getX(), e.getY()))
break;
}
return true;
}
};
private View.OnTouchListener onTouchListener = new View.OnTouchListener() {
@Override
public boolean onTouch(View view, MotionEvent e) {
if (swipedPos < 0) return false;
Point point = new Point((int) e.getRawX(), (int) e.getRawY());
RecyclerView.ViewHolder swipedViewHolder = recyclerView.findViewHolderForAdapterPosition(swipedPos);
View swipedItem = swipedViewHolder.itemView;
Rect rect = new Rect();
swipedItem.getGlobalVisibleRect(rect);
if (e.getAction() == MotionEvent.ACTION_DOWN || e.getAction() == MotionEvent.ACTION_UP ||e.getAction() == MotionEvent.ACTION_MOVE) {
if (rect.top < point.y && rect.bottom > point.y)
gestureDetector.onTouchEvent(e);
else {
recoverQueue.add(swipedPos);
swipedPos = -1;
recoverSwipedItem();
}
}
return false;
}
};
public SwipeHelper(Context context, RecyclerView recyclerView) {
super(0, ItemTouchHelper.LEFT);
this.recyclerView = recyclerView;
this.buttons = new ArrayList<>();
this.gestureDetector = new GestureDetector(context, gestureListener);
this.recyclerView.setOnTouchListener(onTouchListener);
buttonsBuffer = new HashMap<>();
recoverQueue = new LinkedList<Integer>(){
@Override
public boolean add(Integer o) {
if (contains(o))
return false;
else
return super.add(o);
}
};
attachSwipe();
}
@Override
public boolean onMove(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder, RecyclerView.ViewHolder target) {
return false;
}
@Override
public void onSwiped(RecyclerView.ViewHolder viewHolder, int direction) {
int pos = viewHolder.getAdapterPosition();
if (swipedPos != pos)
recoverQueue.add(swipedPos);
swipedPos = pos;
if (buttonsBuffer.containsKey(swipedPos))
buttons = buttonsBuffer.get(swipedPos);
else
buttons.clear();
buttonsBuffer.clear();
swipeThreshold = 0.5f * buttons.size() * BUTTON_WIDTH;
recoverSwipedItem();
}
@Override
public float getSwipeThreshold(RecyclerView.ViewHolder viewHolder) {
return swipeThreshold;
}
@Override
public float getSwipeEscapeVelocity(float defaultValue) {
return 0.1f * defaultValue;
}
@Override
public float getSwipeVelocityThreshold(float defaultValue) {
return 5.0f * defaultValue;
}
@Override
public void onChildDraw(Canvas c, RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder, float dX, float dY, int actionState, boolean isCurrentlyActive) {
int pos = viewHolder.getAdapterPosition();
float translationX = dX;
View itemView = viewHolder.itemView;
if (pos < 0){
swipedPos = pos;
return;
}
if(actionState == ItemTouchHelper.ACTION_STATE_SWIPE){
if(dX < 0) {
List<UnderlayButton> buffer = new ArrayList<>();
if (!buttonsBuffer.containsKey(pos)){
instantiateUnderlayButton(viewHolder, buffer);
buttonsBuffer.put(pos, buffer);
}
else {
buffer = buttonsBuffer.get(pos);
}
translationX = dX * buffer.size() * BUTTON_WIDTH / itemView.getWidth();
drawButtons(c, itemView, buffer, pos, translationX);
}
}
super.onChildDraw(c, recyclerView, viewHolder, translationX, dY, actionState, isCurrentlyActive);
}
private synchronized void recoverSwipedItem(){
while (!recoverQueue.isEmpty()){
int pos = recoverQueue.poll();
if (pos > -1) {
recyclerView.getAdapter().notifyItemChanged(pos);
}
}
}
private void drawButtons(Canvas c, View itemView, List<UnderlayButton> buffer, int pos, float dX){
float right = itemView.getRight();
float dButtonWidth = (-1) * dX / buffer.size();
for (UnderlayButton button : buffer) {
float left = right - dButtonWidth;
button.onDraw(
c,
new RectF(
left,
itemView.getTop(),
right,
itemView.getBottom()
),
pos
);
right = left;
}
}
public void attachSwipe(){
ItemTouchHelper itemTouchHelper = new ItemTouchHelper(this);
itemTouchHelper.attachToRecyclerView(recyclerView);
}
public abstract void instantiateUnderlayButton(RecyclerView.ViewHolder viewHolder, List<UnderlayButton> underlayButtons);
public static class UnderlayButton {
private String text;
private int imageResId;
private int color;
private int pos;
private RectF clickRegion;
private UnderlayButtonClickListener clickListener;
public UnderlayButton(String text, int imageResId, int color, UnderlayButtonClickListener clickListener) {
this.text = text;
this.imageResId = imageResId;
this.color = color;
this.clickListener = clickListener;
}
public boolean onClick(float x, float y){
if (clickRegion != null && clickRegion.contains(x, y)){
clickListener.onClick(pos);
return true;
}
return false;
}
public void onDraw(Canvas c, RectF rect, int pos){
Paint p = new Paint();
// Draw background
p.setColor(color);
c.drawRect(rect, p);
// Draw Text
p.setColor(Color.WHITE);
p.setTextSize(LayoutHelper.getPx(MyApplication.getAppContext(), 12));
Rect r = new Rect();
float cHeight = rect.height();
float cWidth = rect.width();
p.setTextAlign(Paint.Align.LEFT);
p.getTextBounds(text, 0, text.length(), r);
float x = cWidth / 2f - r.width() / 2f - r.left;
float y = cHeight / 2f + r.height() / 2f - r.bottom;
c.drawText(text, rect.left + x, rect.top + y, p);
clickRegion = rect;
this.pos = pos;
}
}
public interface UnderlayButtonClickListener {
void onClick(int pos);
}
}
Usage:
SwipeHelper swipeHelper = new SwipeHelper(this, recyclerView) {
@Override
public void instantiateUnderlayButton(RecyclerView.ViewHolder viewHolder, List<UnderlayButton> underlayButtons) {
underlayButtons.add(new SwipeHelper.UnderlayButton(
"Delete",
0,
Color.parseColor("#FF3C30"),
new SwipeHelper.UnderlayButtonClickListener() {
@Override
public void onClick(int pos) {
// TODO: onDelete
}
}
));
underlayButtons.add(new SwipeHelper.UnderlayButton(
"Transfer",
0,
Color.parseColor("#FF9502"),
new SwipeHelper.UnderlayButtonClickListener() {
@Override
public void onClick(int pos) {
// TODO: OnTransfer
}
}
));
underlayButtons.add(new SwipeHelper.UnderlayButton(
"Unshare",
0,
Color.parseColor("#C7C7CB"),
new SwipeHelper.UnderlayButtonClickListener() {
@Override
public void onClick(int pos) {
// TODO: OnUnshare
}
}
));
}
};
Note：这个辅助类是为向左滑动而设计的。您可以更改滑动方向滑动助手构造函数，并根据 dX 进行更改onChildDraw相应的方法。
如果你想在按钮中显示图像，只需使用图像残差ID in 底层按钮，并重新实施onDraw method.
有一个已知的错误，当您将一个项目从一个项目沿对角线滑动到另一个项目时，第一个触摸的项目会闪烁一点。这可以通过降低值来解决getSwipe 速度阈值，但这使得用户更难滑动该项目。您还可以通过更改其他两个值来调整滑动感觉获取滑动阈值 and getSwipeEscapeVelocity。查看ItemTouchHelper源代码，注释非常有帮助。
我相信还有很多可以优化的地方。如果您想坚持使用 ItemTouchHelper，此解决方案只是提供了一个想法。如果您在使用时遇到问题，请告诉我。下面是一个屏幕截图。
致谢：这个解决方案主要是受到 AdamWei 的回答的启发post