Vaadin 8.2.0：如何在网格单元格中垂直对齐图像

Question

我想在网格中显示缩略图。

这是我的相关代码（简化）：

addColumnVisibilityChangeListener(event -> {
    if (ID_THUMBNAIL.equals(event.getColumn().getId())) {
        if (event.isHidden()) {
            setBodyRowHeight(-1);
        } else {
            setBodyRowHeight(130);
        }
        // needed to force rendering of current values
        getDataProvider().refreshAll();
    }
});
// rescale returns a (cached) ExternalResource, image is 120x120px max
// aspect ratio is preserved, so at least width or height is 120px
grid.addColumn(this::rescale, new ImageRenderer<>(this::showImage))
    .setCaption(ID_THUMBNAIL)
    .setStyleGenerator(r -> ID_THUMBNAIL)
    .setWidth(131);

CSS 是：

.asset-grid td.thumbnail {
  // height is set bij Vaadin Grid
  padding: 5px;
  text-align: center !important;    
}
.asset-grid td.thumbnail img {
  vertical-align: middle !important;
}

除了缩略图图像的垂直对齐之外，一切正常。它显示在单元格的顶部。我尝试了几种设置，但没有任何效果。

Answer 1

这主要基于this answer on how to vertical-align image in div，通过反复试验进行了一些细微的变化。

可以将原始答案与fixed line-size（例如130）和vertical-align: middle 一起使用，但无论您设置什么高度（在chrome 和edge 中测试），更新版本都提供了灵活性。

代码：

import com.vaadin.event.ShortcutAction;
import com.vaadin.server.ExternalResource;
import com.vaadin.server.Resource;
import com.vaadin.ui.*;
import com.vaadin.ui.renderers.ClickableRenderer;
import com.vaadin.ui.renderers.ImageRenderer;

public class GridWithImages extends VerticalLayout {

    public GridWithImages() {
        // basic grid setup
        Grid<User> grid = new Grid<>();
        grid.addColumn(User::getId)
            .setCaption("Id");
        Grid.Column<User, Resource> thumbnailColumn = grid.addColumn(User::getThumbnail)
                                                          .setCaption("Thumbnail")
                                                          .setRenderer(new ImageRenderer<>(this::showImage))
                                                          .setStyleGenerator(r -> "thumbnail")
                                                          .setWidth(131);
        grid.setItems(new User(1), new User(2), new User(3));
        grid.setBodyRowHeight(130);

        // allow to easily update height and width for testing purposes
        TextField rowHeightField = new TextField("Row height", "130");
        TextField thumbnailColumnWidthField = new TextField("Thumbnail width", "131");
        Button button = new Button("Update", event -> {
            // NOT SAFE, NOT ELEGANT, but for the sake of brevity just use those values...
            grid.setBodyRowHeight(Integer.valueOf(rowHeightField.getValue()));
            thumbnailColumn.setWidth(Integer.valueOf(thumbnailColumnWidthField.getValue()));
        });
        button.setClickShortcut(ShortcutAction.KeyCode.ENTER);

        addComponents(grid, rowHeightField, thumbnailColumnWidthField, button);
    }

    // image renderer click handler
    private void showImage(ClickableRenderer.RendererClickEvent<User> event) {
        Notification.show("This will be the actual image in full size... maybe, maybe not!");
    }

    // basic bean for easy binding
    private class User {
        private int id;
        private Resource thumbnail = new ExternalResource("https://www.gravatar.com/avatar/d9269818df2a058ad6bf9dbbaf1e8240?s=32&d=identicon&r=PG");

        public User(int id) {
            this.id = id;
        }

        public int getId() {
            return id;
        }

        public void setId(int id) {
            this.id = id;
        }

        public Resource getThumbnail() {
            return thumbnail;
        }

        public void setThumbnail(Resource thumbnail) {
            this.thumbnail = thumbnail;
        }
    }
}

主题：

td.v-grid-cell.thumbnail > img {
  vertical-align: unset; // leaving it centered as inherited, shifts the image a few pixels downwards
  position: relative;
  left: 50%;
  top: 50%;
  transform: translate(-50%, -50%); // https://stackoverflow.com/questions/34551381/is-the-css3-transform-translate-percentage-values-relative-to-its-width-and-or-h
}

结果：