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[英]Why doesn't this control update its contents while the background thread is executing?
[英]Why custom control doesn't resize with its children?
考虑以下最小的可重现示例:
public class Launcher extends Application {
public static final double SCENE_SIZE = 500;
@Override
public void start(Stage primaryStage) {
GridPane grid = new GridPane();
grid.setHgap(10);
grid.setVgap(10);
grid.setGridLinesVisible(true);
grid.getColumnConstraints().setAll(
new ColumnConstraints(USE_COMPUTED_SIZE, USE_COMPUTED_SIZE, USE_COMPUTED_SIZE, Priority.NEVER, HPos.LEFT, false),
new ColumnConstraints(USE_COMPUTED_SIZE, USE_COMPUTED_SIZE, USE_COMPUTED_SIZE, Priority.ALWAYS, HPos.LEFT, false)
);
grid.getRowConstraints().setAll(
new RowConstraints(USE_COMPUTED_SIZE, USE_COMPUTED_SIZE, USE_COMPUTED_SIZE, Priority.NEVER, VPos.TOP, false),
new RowConstraints(USE_COMPUTED_SIZE, USE_COMPUTED_SIZE, USE_COMPUTED_SIZE, Priority.NEVER, VPos.TOP, false),
new RowConstraints(USE_COMPUTED_SIZE, USE_COMPUTED_SIZE, USE_COMPUTED_SIZE, Priority.NEVER, VPos.TOP, false)
);
CustomControl customControl = new CustomControl("Lorem Ipsum ".repeat(10));
customControl.prefWidthProperty().bind(grid.widthProperty());
TextFlow textFlow = new TextFlow(new Text("Lorem Ipsum ".repeat(10)));
textFlow.prefWidthProperty().bind(grid.widthProperty());
grid.add(new Label("0"), 0, 0);
grid.add(customControl, 1, 0);
grid.add(new Label("1"), 0, 1);
grid.add(textFlow, 1, 1);
grid.add(new Label("2"), 0, 2);
grid.add(new Label("..."), 1, 2);
Scene scene = new Scene(grid, SCENE_SIZE, SCENE_SIZE);
primaryStage.setTitle("Demo");
primaryStage.setScene(scene);
primaryStage.setOnCloseRequest(t -> Platform.exit());
primaryStage.show();
}
static class CustomControl extends Control {
private final StringProperty text = new SimpleStringProperty();
public CustomControl(String text) { setText(text); }
public String getText() { return text.get(); }
public StringProperty textProperty() { return text; }
public void setText(String text) { this.text.set(text); }
@Override
protected Skin<?> createDefaultSkin() { return new CustomControlSkin(this); }
}
static class CustomControlSkin extends SkinBase<CustomControl> {
TextFlow textFlow;
public CustomControlSkin(CustomControl control) {
super(control);
textFlow = new TextFlow();
textFlow.getChildren().setAll(new Text(control.getText()));
control.textProperty().addListener(
(obs, old, value) -> textFlow.getChildren().setAll(new Text(control.getText()))
);
control.heightProperty().addListener((observable, oldValue, newValue) -> System.out.println("control = " + newValue));
textFlow.heightProperty().addListener((observable, oldValue, newValue) -> { System.out.println("textFlow = " + newValue); });
getChildren().setAll(textFlow);
}
}
}
Window 调整大小会触发 TextFlow 自动换行,因此 TextFlow 会更改其高度。 问题是它不会导致 CustomControl 高度变化,它保持不变(注意控制台输出)。
同时,下一个网格行上的“纯”TextFlow 的行为正是 CustomControl 所期望的。 当 window 调整大小时,它会来回更改其高度(以及 GridPane 行高)。
我认为任何控件都会根据孩子的高度自动改变自己的高度(SkinBase 包含很多方法),但似乎我错了。 简单地在 TextFlow 监听器中设置控制高度是没有帮助的,因为这样只能增加它。
更新:
好的,我找到了问题所在。 发生这种情况是因为 TextFlow 需要实际宽度来计算其首选高度,但 SkinBase 使用负宽度值。 解决方案:
control.widthProperty().addListener((observable, oldValue, newValue) -> {
control.setPrefHeight(textFlow.prefHeight(newValue.doubleValue()));
});
如果有更好的方法欢迎分享:)
更新 2:
根据@Slaw 的建议,这个也可以。 奇怪的是width
arg 值总是-1
,所以我们必须从 skinnable 中获取宽度值。
static class CustomControlSkin extends SkinBase<CustomControl> {
// ...
@Override
protected double computePrefHeight(double width, double topInset, double rightInset, double bottomInset,
double leftInset) {
return textFlow.prefHeight(getSkinnable().getWidth() != 0 ? getSkinnable().getWidth() : -1);
}
@Override
protected double computeMaxHeight(double width, double topInset, double rightInset, double bottomInset,
double leftInset) {
return computePrefHeight(width, topInset, rightInset, bottomInset, leftInset);
}
}
根据@Slaw 的建议,这是一种可能的解决方案。 奇怪的是width
arg 值总是-1
,所以我们必须从 skinnable 中获取宽度值。
static class CustomControlSkin extends SkinBase<CustomControl> {
// ...
@Override
protected double computePrefHeight(double width, double topInset, double rightInset, double bottomInset,
double leftInset) {
return textFlow.prefHeight(getSkinnable().getWidth() != 0 ? getSkinnable().getWidth() : -1);
}
@Override
protected double computeMaxHeight(double width, double topInset, double rightInset, double bottomInset,
double leftInset) {
return computePrefHeight(width, topInset, rightInset, bottomInset, leftInset);
}
}
每次 Control 宽度更改时,它都会调用computeMaxHeight()
,它只是将计算委托给SkinBase
。 然后我们只是强制 Control 始终使用 TextFlow 首选项高度。
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