RecyclerView - 跳过第一个布局传递的屏幕外项目

Question

我的一个适配器出了问题.我有一系列图像,我在网格中显示如下:

当我有一个单一屏幕的物品并且它们都显示正常时,这很有效.当有更多项目向下滚动时,会出现问题.最初当我向下滚动时,项目显示为空白,GridLayout容器在那里,显示图像的代码运行,但它们不会出现在屏幕上,如下所示:

如果我向上滚动,然后再次向下滚动,图像会显示在它们应该的位置:

看起来我需要刷新布局或告诉渲染器某些东西已经发生变化,但我尝试的任何东西似乎都没有做任何事情.我试过打电话requestLayout,invalidate但它似乎没有解决问题.我还注册了一个GlobalOnLayoutListener,但这并没有更好.

这是相关代码:

这是我的onBindViewHolder方法

final GridLayout grid = ((KKAlbumViewHolder) holder).mGridLayout;
grid.removeAllViews();
int width = grid.getWidth();
if(width > 0) {
    albumHolder.setPreviewImages(posts);
}else {
    albumHolder.itemView.addOnLayoutChangeListener(new View.OnLayoutChangeListener() {
                @Override
                public void onLayoutChange(View v, int left, int top, int right, int bottom, int oldLeft, int oldTop, int oldRight, int oldBottom) {
                    albumHolder.itemView.removeOnLayoutChangeListener(this);
                    albumHolder.setPreviewImages(posts);
                    albumHolder.mGridLayout.invalidate();
                }
    });
}

这是我用来布局图像的方法.它基本上将图像放在不规则的网格中,因此如果有长图像或高图像,该图像将尝试占据整行或整列,具体取决于空闲空间.我设置参数宽度和高度的原因是毕加索不抱怨该.fit()方法:

public void setPreviewImages(ArrayList<KKPost> posts) {
        Picasso picasso = Picasso.with(itemView.getContext());

        int space = 0;
        int tl = 1 << 0;
        int tr = 1 << 1;
        int bl = 1 << 2;
        int br = 1 << 3;
        int lCol = tl | bl;
        int rCol = tr | br;
        int tRow = tl | tr;
        int bRow = bl | br;
        int full = lCol | rCol;
        boolean hasLongImage = false;
        for(KKPost post : posts) {
            if(space == full){
                break;
            }

            int margin = 2;

            ImageView view = new ImageView(itemView.getContext());
            GridLayout.LayoutParams param = new GridLayout.LayoutParams();
            view.setBackgroundColor(Color.LTGRAY);
            if(posts.size() < 4){
                param.columnSpec = GridLayout.spec(0, 2);
                param.rowSpec = GridLayout.spec(0, 2);
                param.width = mGridLayout.getWidth();
                param.height = mGridLayout.getHeight();
                mGridLayout.addView(view, param);
                picasso.load(post.url).fit().centerCrop().into(view);
                break;
            }

            if (post.aspectRatio >= 1.2 && !hasLongImage) {
                //landscape
                if((space & tRow) == 0){
                    param.rowSpec = GridLayout.spec(0, 1);
                    param.columnSpec = GridLayout.spec(0, 2);
                    param.height = mGridLayout.getHeight()/2;
                    param.width = mGridLayout.getWidth();
                    param.bottomMargin = margin;
                    space |= tRow;
                    mGridLayout.addView(view, param);
                    picasso.load(post.url).fit().centerCrop().into(view);
                    hasLongImage = true;
                    continue;
                }
                if((space & bRow) == 0){
                    param.rowSpec = GridLayout.spec(1, 1);
                    param.columnSpec = GridLayout.spec(0, 2);
                    param.height = mGridLayout.getHeight()/2;
                    param.width = mGridLayout.getWidth();
                    param.topMargin = margin;
                    space |= bRow;
                    mGridLayout.addView(view, param);
                    picasso.load(post.url).fit().centerCrop().into(view);
                    hasLongImage = true;
                    continue;
                }
            } else if (post.aspectRatio <= 0.8 && post.aspectRatio > 0 && !hasLongImage) {
                //portrait
                if((space & lCol) == 0){
                    param.columnSpec = GridLayout.spec(0, 1);
                    param.rowSpec = GridLayout.spec(0, 2);
                    param.height = mGridLayout.getHeight();
                    param.width = mGridLayout.getWidth()/2;
                    param.rightMargin = margin;
                    space |=  lCol;
                    mGridLayout.addView(view, param);
                    picasso.load(post.url).fit().centerCrop().into(view);
                    hasLongImage = true;
                    continue;
                }
                if((space & rCol) == 0){
                    param.columnSpec = GridLayout.spec(1, 1);
                    param.rowSpec = GridLayout.spec(0, 2);
                    param.height = mGridLayout.getHeight();
                    param.width = mGridLayout.getWidth()/2;
                    param.leftMargin = margin;
                    space |= rCol;
                    mGridLayout.addView(view, param);
                    picasso.load(post.url).fit().centerCrop().into(view);
                    hasLongImage = true;
                    continue;
                }
            }
            //square or no space or unknown
            if((space & tl) == 0){
                param.columnSpec = GridLayout.spec(0,1);
                param.rowSpec = GridLayout.spec(0,1);
                space |= tl;
                param.bottomMargin = margin;
                param.rightMargin = margin;
            }else
            if((space & tr) == 0) {
                param.columnSpec = GridLayout.spec(1,1);
                param.rowSpec = GridLayout.spec(0,1);
                space |= tr;
                param.bottomMargin = margin;
                param.leftMargin = margin;
            }else
            if((space & bl) == 0){
                param.columnSpec = GridLayout.spec(0,1);
                param.rowSpec = GridLayout.spec(1,1);
                space |= bl;
                param.rightMargin = margin;
                param.topMargin = margin;
            }else
            if((space & br) == 0){
                param.columnSpec = GridLayout.spec(1,1);
                param.rowSpec = GridLayout.spec(1,1);
                space |= br;
                param.leftMargin = margin;
                param.topMargin = margin;
            }
            param.height = mGridLayout.getHeight()/2;
            param.width = mGridLayout.getWidth()/2;
            mGridLayout.addView(view, param);
            picasso.load(post.url).fit().centerCrop().into(view);
        }
    }
}

为什么这似乎跳过了最初不可见的项目的第一个渲染过程？

编辑:我做了一些重构,所以我可以重新使用imageviews而不是删除/创建新的,并发现为这些项添加的视图不会得到onLayoutChange回调.所有其他项目都获得onLayoutChange回调,并且像以前一样,最初没有得到呼叫的项目,在我向上滚动并再次向下滚动后获取它.看到:

view.addOnLayoutChangeListener(new View.OnLayoutChangeListener() {
                @Override
                public void onLayoutChange(View v, int left, int top, int right, int bottom, int oldLeft, int oldTop, int oldRight, int oldBottom) {
                    view.removeOnLayoutChangeListener(this);
                    picasso.load(post.url).into(view);
                }
            });

编辑:11月15日

这是viewholder布局的xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.v7.widget.CardView
    android:id="@+id/album_card_view"
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:card_view="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_gravity="center"
    card_view:cardCornerRadius="@dimen/feed_card_corner_radius"
    card_view:cardElevation="@dimen/cardview_default_elevation"
    card_view:cardMaxElevation="@dimen/cardview_default_elevation"
    card_view:cardUseCompatPadding="true"
    xmlns:autofit="http://schemas.android.com/apk/res-auto"
    xmlns:app="http://schemas.android.com/apk/res-auto">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical">

        <android.support.percent.PercentRelativeLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:id="@+id/percent_layout">

            <GridLayout
                android:background="@color/white"
                android:id="@+id/preview_grid_layout"
                android:columnCount="2"
                android:rowCount="2"
                android:alignmentMode="alignBounds"
                android:layout_height="0dp"
                android:layout_width="0dp"
                app:layout_widthPercent="100%"
                app:layout_aspectRatio="100%">

            </GridLayout>

        </android.support.percent.PercentRelativeLayout>

        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:padding="@dimen/card_padding_4dp"
            android:orientation="vertical">

            <TextView
                android:id="@+id/album_title"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                tools:text="Family Photos"/>

         </LinearLayout>

    </LinearLayout>

</android.support.v7.widget.CardView>

Answer 1

检查你是否有setHasStableIds(true)，如果你这样做了，你必须重写getItemId(int position)为每个视图指定id。如果你不这样做，后续的onBindViewholders()调用将不会触发，你的视图也不会更新