使用Android的RecyclerView时,在刷卡行下添加带有文本/图标的彩色背景

Question

编辑:真正的问题是我LinearLayout被另一个布局包裹,导致不正确的行为.Sanvywell接受的答案有一个更好,更完整的例子,说明如何在刷卡视图下绘制颜色,而不是我在问题中提供的代码片段.

现在,在ItemTouchHelper类的帮助下,RecyclerView小部件本身支持行扫描,我试图在应用程序中使用它,行的行为与Google的收件箱应用程序类似.也就是说,向左侧滑动执行一个动作,向右滑动则执行另一个动作.

使用ItemTouchHelper.SimpleCallback的onSwiped方法很容易实现动作本身.但是,我无法找到一种简单的方法来设置应该出现在当前正在刷卡的视图下方的颜色和图标(例如在谷歌的收件箱应用程序中).

要做到这一点,我试图覆盖ItemTouchHelper.SimpleCallback的onChildDraw方法,如下所示:

@Override
public void onChildDraw(Canvas c, RecyclerView recyclerView,
                        RecyclerView.ViewHolder viewHolder, float dX, float dY,
                        int actionState, boolean isCurrentlyActive) {
    RecyclerViewAdapter.ViewHolder vh = (RecyclerViewAdapter.ViewHolder) viewHolder;
    LinearLayout ll = vh.linearLayout;

    Paint p = new Paint();
    if(dX > 0) {
        p.setARGB(255, 255, 0, 0);
    } else {
        p.setARGB(255, 0, 255, 0);
    }

    c.drawRect(ll.getLeft(), ll.getTop(), ll.getRight(), ll.getBottom(), p);

    super.onChildDraw(c, recyclerView, viewHolder, dX, dY, actionState, isCurrentlyActive);
}

从dX确定滑动方向并设置适当的颜色按预期工作,但我从中获得的坐标ViewHolder始终对应于第一个LinearLayout充气的位置.

如何获得LinearLayout当前滑动行中的正确坐标？是否有更简单的方法(不需要覆盖onChildDraw)来设置背景颜色和图标？

Answer 1

我也在努力实现这个功能,但是你引导我朝着正确的方向前进.

@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) {
        // Get RecyclerView item from the ViewHolder
        View itemView = viewHolder.itemView;

        Paint p = new Paint();
        if (dX > 0) {
            /* Set your color for positive displacement */

            // Draw Rect with varying right side, equal to displacement dX
            c.drawRect((float) itemView.getLeft(), (float) itemView.getTop(), dX,
                    (float) itemView.getBottom(), p);
        } else {
            /* Set your color for negative displacement */

            // Draw Rect with varying left side, equal to the item's right side plus negative displacement dX
            c.drawRect((float) itemView.getRight() + dX, (float) itemView.getTop(),
                    (float) itemView.getRight(), (float) itemView.getBottom(), p);
        }

        super.onChildDraw(c, recyclerView, viewHolder, dX, dY, actionState, isCurrentlyActive);
    }
}

Answer 2

接受的答案很好地为背景着色,但没有解决绘制图标的问题.

这对我有用,因为它既设置了背景颜色又绘制了图标,在滑动过程中没有拉伸图标,或者在滑动后在前一个和下一个项目之间留下间隙.

public static final float ALPHA_FULL = 1.0f;

public void onChildDraw(Canvas c, RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder, float dX, float dY, int actionState, boolean isCurrentlyActive) {
    if (actionState == ItemTouchHelper.ACTION_STATE_SWIPE) {
        // Get RecyclerView item from the ViewHolder
        View itemView = viewHolder.itemView;

        Paint p = new Paint();
        Bitmap icon;

        if (dX > 0) {
            /* Note, ApplicationManager is a helper class I created 
               myself to get a context outside an Activity class - 
               feel free to use your own method */

            icon = BitmapFactory.decodeResource(
                    ApplicationManager.getContext().getResources(), R.drawable.myleftdrawable);

            /* Set your color for positive displacement */
            p.setARGB(255, 255, 0, 0);

            // Draw Rect with varying right side, equal to displacement dX
            c.drawRect((float) itemView.getLeft(), (float) itemView.getTop(), dX,
                    (float) itemView.getBottom(), p);

            // Set the image icon for Right swipe
            c.drawBitmap(icon,
                    (float) itemView.getLeft() + convertDpToPx(16),
                    (float) itemView.getTop() + ((float) itemView.getBottom() - (float) itemView.getTop() - icon.getHeight())/2,
                    p);
        } else {
            icon = BitmapFactory.decodeResource(
                    ApplicationManager.getContext().getResources(), R.drawable.myrightdrawable);

            /* Set your color for negative displacement */
            p.setARGB(255, 0, 255, 0);

            // Draw Rect with varying left side, equal to the item's right side
            // plus negative displacement dX
            c.drawRect((float) itemView.getRight() + dX, (float) itemView.getTop(),
                    (float) itemView.getRight(), (float) itemView.getBottom(), p);

            //Set the image icon for Left swipe
            c.drawBitmap(icon,
                    (float) itemView.getRight() - convertDpToPx(16) - icon.getWidth(),
                    (float) itemView.getTop() + ((float) itemView.getBottom() - (float) itemView.getTop() - icon.getHeight())/2,
                    p);
        }

        // 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);
    }
}

private int convertDpToPx(int dp){
    return Math.round(dp * (getResources().getDisplayMetrics().xdpi / DisplayMetrics.DENSITY_DEFAULT));
}

Answer 3

这是我在没有 3rd 方库的情况下如何做到的。

前景视图将始终在回收器视图中可见，并且当执行滑动时，背景将保持在静态位置可见。

创建您的自定义 RecyclerView 项目并将您的自定义图标、文本和背景颜色添加到项目的背景布局中。请注意，我在RelativeLayoutwithid=foreground和 中放置了一个 id id=background。

这是我的recylerview_item.xml。

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:orientation="vertical">

    <RelativeLayout
        android:id="@+id/background"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:background="@color/colorPrimary"> <!--Add your background color here-->

        <ImageView
            android:id="@+id/delete_icon"
            android:layout_width="30dp"
            android:layout_height="30dp"
            android:layout_alignParentRight="true"
            android:layout_centerVertical="true"
            android:layout_marginRight="10dp"
            app:srcCompat="@drawable/ic_delete"/>

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_centerVertical="true"
            android:layout_marginRight="10dp"
            android:layout_toLeftOf="@id/delete_icon"
            android:text="Swipe to delete"
            android:textColor="#fff"
            android:textSize="13dp" />
    </RelativeLayout>

    <RelativeLayout
        android:padding="20dp"
        android:id="@+id/foreground"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:background="@color/colorWhite">

            <TextView
                android:id="@+id/textView"
                android:text="HelloWorld"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content" />

    </RelativeLayout>
</FrameLayout>

并从您ViewHolder定义您RelativeLayout foreground并background view公开。还要创建一个将删除项目的方法。在我的情况下，我的 ViewHolder 在我的之下RecyclerViewAdapter.class，所以......

public class RecyclerViewAdapter extends RecyclerView.Adapter<RecyclerViewAdapter.ViewHolder> {

    List<Object> listItem;

    public RecyclerViewAdapter(...) {
        ...
    } 

    @Override
    public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View view = mInflater.inflate(R.layout.recyclerview_item, parent, false);
        return new ViewHolder(view);
    }

    @Override
    public void onBindViewHolder(final ViewHolder holder, int position) {
        ....
    }

    @Override
    public int getItemCount() {
        ...
    }

    public class ViewHolder extends RecyclerView.ViewHolder{

        public RelativeLayout foreground, background;

        public ViewHolder(View itemView) {
            super(itemView);

            /** define your foreground and background **/

            foreground = itemView.findViewById(R.id.foreground);
            background = itemView.findViewById(R.id.background);

        }

    }

    /**Call this later to remove the item on swipe**/
    public void removeItem(int position){
        //remove the item here
        listItem.remove(position);
        notifyItemRemoved(position);
    }
}

并创建一个类并命名它RecyclerItemTouchHelper.class，这就是滑动的地方。

public class RecyclerItemTouchHelper extends ItemTouchHelper.SimpleCallback {

    private RecyclerItemTouchHelperListener listener;

    public RecyclerItemTouchHelper(int dragDirs, int swipeDirs, RecyclerItemTouchHelperListener listener) {
        super(dragDirs, swipeDirs);
        this.listener = listener;
    }

    @Override
    public boolean onMove(@NonNull RecyclerView recyclerView, @NonNull RecyclerView.ViewHolder viewHolder, @NonNull RecyclerView.ViewHolder target) {
        return true;
    }

    @Override
    public void onSelectedChanged(RecyclerView.ViewHolder viewHolder, int actionState) {
        if (viewHolder != null) {
            final View foregroundView = ((RecyclerViewAdapter.ViewHolder) viewHolder).foreground;
            getDefaultUIUtil().onSelected(foregroundView);
        }
    }

    @Override
    public void onChildDrawOver(Canvas c, RecyclerView recyclerView,
                                RecyclerView.ViewHolder viewHolder, float dX, float dY,
                                int actionState, boolean isCurrentlyActive) {
        final View foregroundView = ((RecyclerViewAdapter.ViewHolder) viewHolder).foreground;
        getDefaultUIUtil().onDrawOver(c, recyclerView, foregroundView, dX, dY,
                actionState, isCurrentlyActive);
    }

    @Override
    public void clearView(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder) {
        final View foregroundView = ((RecyclerViewAdapter.ViewHolder) viewHolder).foreground;
        getDefaultUIUtil().clearView(foregroundView);
    }

    @Override
    public void onChildDraw(Canvas c, RecyclerView recyclerView,
                            RecyclerView.ViewHolder viewHolder, float dX, float dY,
                            int actionState, boolean isCurrentlyActive) {
        final View foregroundView = ((RecyclerViewAdapter.ViewHolder) viewHolder).foreground;

        getDefaultUIUtil().onDraw(c, recyclerView, foregroundView, dX, dY,
                actionState, isCurrentlyActive);
    }

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

    @Override
    public int convertToAbsoluteDirection(int flags, int layoutDirection) {
        return super.convertToAbsoluteDirection(flags, layoutDirection);
    }

    public interface RecyclerItemTouchHelperListener {
        void onSwiped(RecyclerView.ViewHolder viewHolder, int direction, int position);
    }
}

现在，从您MainActivity.class或您所在的任何地方RecyclerView，将其附加RecyclerItemTouchHelper到其中。在我的情况下，RecyclerView 在，MainActivity.class所以我实现RecyclerItemTouchHelper.RecyclerItemTouchHelperListener了它并覆盖了该方法onSwiped()......

public class MainActivity extends AppCompatActivity implements RecyclerItemTouchHelper.RecyclerItemTouchHelperListener {

    RecyclerView recyclerView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Toolbar toolbar = findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        //Configure RecyclerView

        recyclerView = (RecyclerView) findViewById(R.id.recyclerView);  
        RecyclerView.LayoutManager mLyoutManager = new LinearLayoutManager(getApplicationContext());
        recyclerView.setLayoutManager(mLyoutManager);
        recyclerView.setItemAnimator(new DefaultItemAnimator());
        adapter = new RecyclerViewAdapter(this);
        adapter.setClickListener(this);
        recyclerView.setAdapter(adapter);
        recyclerView.addItemDecoration(new DividerItemDecoration(recyclerView.getContext(), DividerItemDecoration.VERTICAL));

        //Attached the ItemTouchHelper
        ItemTouchHelper.SimpleCallback itemTouchHelperCallback = new RecyclerItemTouchHelper(0, ItemTouchHelper.LEFT, this);
        new ItemTouchHelper(itemTouchHelperCallback).attachToRecyclerView(recyclerView);
    }

    //define the method onSwiped()
    @Override
    public void onSwiped(RecyclerView.ViewHolder viewHolder, int direction, int position) {
        if (viewHolder instanceof RecyclerViewAdapter.ViewHolder) {
            adapter.removeItem(viewHolder.getAdapterPosition()); //remove the item from the adapter
        }
    }

}

有关更多信息和说明，请访问它的博客。

Answer 4

对于仍然发现此默认值的人来说，这是最简单的方法。

一个简单的实用程序类，用于在向左或向右滑动时向 RecyclerView 项目添加背景、图标和标签。

插入到 Gradle

implementation 'it.xabaras.android:recyclerview-swipedecorator:1.1'

覆盖 ItemTouchHelper 类的 onChildDraw 方法

@Override
public void onChildDraw (Canvas c, RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder,float dX, float dY,int actionState, boolean isCurrentlyActive){
    new RecyclerViewSwipeDecorator.Builder(MainActivity.this, c, recyclerView, viewHolder, dX, dY, actionState, isCurrentlyActive)
            .addBackgroundColor(ContextCompat.getColor(MainActivity.this, R.color.my_background))
            .addActionIcon(R.drawable.my_icon)
            .create()
            .decorate();

    super.onChildDraw(c, recyclerView, viewHolder, dX, dY, actionState, isCurrentlyActive);
}

了解更多信息 -> https://github.com/xabaras/RecyclerViewSwipeDecorator

Answer 5

我不确定这些解决方案(@Sanvywell,@ HappyKatz和@ user2410066)是如何为你们工作的,但在我的情况下我需要另外检查onChildDraw方法.

看起来像ItemTouchHelper保留ViewHolder被删除的行,以防需要恢复.onChildDraw除了正在刷的VH之外,它还要求那些VH.不确定此行为的内存管理含义,但我需要在开始时onChildDraw进行额外的检查,以避免绘制"fantom"行.

if (viewHolder.getAdapterPosition() == -1) {
    return;
}

奖金部分:

我也想继续绘制其他行动画到新位置的行刷卡删除后,我不能内做ItemTouchHelper和onChildDraw.最后我不得不添加另一个项目装饰器来做到这一点.它遵循这些方针:

public void onDraw(Canvas c, RecyclerView parent, RecyclerView.State state) {
    if (parent.getItemAnimator().isRunning()) {
        // find first child with translationY > 0
        // draw from it's top to translationY whatever you want

        int top = 0;
        int bottom = 0;

        int childCount = parent.getLayoutManager().getChildCount();
        for (int i = 0; i < childCount; i++) {
            View child = parent.getLayoutManager().getChildAt(i);
            if (child.getTranslationY() != 0) {
                top = child.getTop();
                bottom = top + (int) child.getTranslationY();                    
                break;
            }
        }

        // draw whatever you want

        super.onDraw(c, parent, state);
    }
}

更新:我写了一篇关于回收器视图滑动的博客文章删除功能.有人可能会发现它很有用.不需要第三方库.

博客文章 git repo

Answer 6

HappyKatz解决方案有一个棘手的bug.当dX == 0时,是否有任何理由绘制位图？在某些情况下,这会导致列表项上方的永久图标可见性 当您只是触摸列表项并且dX == 1时,图标也会在列表项上方显示.解决这些问题:

        if (dX > rectOffset) {
            c.drawRect((float) itemView.getLeft(), (float) itemView.getTop(), dX,
                    (float) itemView.getBottom(), leftPaint);
            if (dX > iconOffset) {
                c.drawBitmap(leftBitmap,
                        (float) itemView.getLeft() + padding,
                        (float) itemView.getTop() + ((float) itemView.getBottom() - (float) itemView.getTop() - leftBitmap.getHeight()) / 2,
                        leftPaint);
            }
        } else if (dX < -rectOffset) {
            c.drawRect((float) itemView.getRight() + dX, (float) itemView.getTop(),
                    (float) itemView.getRight(), (float) itemView.getBottom(), rightPaint);
            if (dX < -iconOffset) {
                c.drawBitmap(rightBitmap,
                        (float) itemView.getRight() - padding - rightBitmap.getWidth(),
                        (float) itemView.getTop() + ((float) itemView.getBottom() - (float) itemView.getTop() - rightBitmap.getHeight()) / 2,
                        rightPaint);
            }
        }

Answer 7

为了实现，我使用了 Marcin Kitowicz 创建的示例代码（此处）。

该解决方案的优点：

1. 使用具有布局边界的背景视图，而不是创建将显示在任何位图或可绘制对象顶部的矩形。
2. 使用与位图相反的可绘制图像，比将可绘制图像转换为位图更容易实现。

原始的实现代码可以在这里找到。为了实现向左滑动，我使用了反向左右定位逻辑。

override fun onChildDraw(c: Canvas, recyclerView: RecyclerView, viewHolder: RecyclerView.ViewHolder, dX: Float, dY: Float, actionState: Int, isCurrentlyActive: Boolean) {
if (actionState == ItemTouchHelper.ACTION_STATE_SWIPE) {
    var icon = ContextCompat.getDrawable(context!!, R.drawable.ic_save_24dp)
    var iconLeft = 0
    var iconRight = 0

    val background: ColorDrawable
    val itemView = viewHolder.itemView
    val margin = convertDpToPx(32)
    val iconWidth = icon!!.intrinsicWidth
    val iconHeight = icon.intrinsicHeight
    val cellHeight = itemView.bottom - itemView.top
    val iconTop = itemView.top + (cellHeight - iconHeight) / 2
    val iconBottom = iconTop + iconHeight

    // Right swipe.
    if (dX > 0) {
        icon = ContextCompat.getDrawable(context!!, R.drawable.ic_save_24dp)
        background = ColorDrawable(Color.RED)
        background.setBounds(0, itemView.getTop(), (itemView.getLeft() + dX).toInt(), itemView.getBottom())
        iconLeft = margin
        iconRight = margin + iconWidth
    } /*Left swipe.*/ else {
        icon = ContextCompat.getDrawable(context!!, R.drawable.ic_save_24dp)
        background = ColorDrawable(Color.BLUE)
        background.setBounds((itemView.right - dX).toInt(), itemView.getTop(), 0, itemView.getBottom())
        iconLeft = itemView.right - margin - iconWidth
        iconRight = itemView.right - margin
    }
    background.draw(c)
    icon?.setBounds(iconLeft, iconTop, iconRight, iconBottom)
    icon?.draw(c)
    super.onChildDraw(c, recyclerView, viewHolder, dX, dY, actionState, isCurrentlyActive)
}
}