Why "No com.badlogic.gdx.scenes.scene2d.ui.ScrollPane$ScrollPaneStyle registered with name: default" error is coming and how to fix it?

Question

When I am compiling LibGdx project I am getting the below exception.

My question here is why it is coming and how to resolve this?

Libgdx: 0.9.9

com.badlogic.gdx.utils.GdxRuntimeException: No com.badlogic.gdx.scenes.scene2d.ui.ScrollPane$ScrollPaneStyle registered with name: default

Json File

{
com.badlogic.gdx.graphics.g2d.BitmapFont: { default-font: { file: default.fnt } },
com.badlogic.gdx.graphics.Color: {
    green: { a: 1, b: 0, g: 1, r: 0 },
    white: { a: 1, b: 1, g: 1, r: 1 },
    red: { a: 1, b: 0, g: 0, r: 1 },
    black: { a: 1, b: 0, g: 0, r: 0 }
},
com.badlogic.gdx.scenes.scene2d.ui.Skin$TintedDrawable: {
    dialogDim: { name: white, color: { r: 0, g: 0, b: 0, a: 0.45 } }
},
com.badlogic.gdx.scenes.scene2d.ui.Button$ButtonStyle: {
    default: { down: default-round-down, up: default-round },
    toggle: { down: default-round-down, checked: default-round-down, up: default-round }
},
com.badlogic.gdx.scenes.scene2d.ui.TextButton$TextButtonStyle: {
    default: { down: default-round-down, up: default-round, font: default-font, fontColor: white },
    toggle: { down: default-round-down, up: default-round, checked: default-round-down, font: default-font, fontColor: white, downFontColor: red }
},
com.badlogic.gdx.scenes.scene2d.ui.SelectBox$SelectBoxStyle: {
    default: { font: default-font, fontColor: white, background: default-select, scrollStyle: default, listStyle: { font: default-font, selection: default-select-selection } }
},
com.badlogic.gdx.scenes.scene2d.ui.SplitPane$SplitPaneStyle: {
    default-vertical: { handle: default-splitpane-vertical },
    default-horizontal: { handle: default-splitpane }
},
com.badlogic.gdx.scenes.scene2d.ui.ScrollPane$ScrollPaneStyle: {
    default: { vScroll: default-scroll, hScrollKnob: default-round-large, background: default-rect, hScroll: default-scroll, vScrollKnob: default-round-large }
},
com.badlogic.gdx.scenes.scene2d.ui.Window$WindowStyle: {
    default: { titleFont: default-font, background: default-window, titleFontColor: white },
    dialog: { titleFont: default-font, background: default-window, titleFontColor: white, stageBackground: dialogDim }
},
com.badlogic.gdx.scenes.scene2d.ui.Slider$SliderStyle: {
    default-horizontal: { background: default-slider, knob: default-slider-knob }
},
com.badlogic.gdx.scenes.scene2d.ui.Label$LabelStyle: {
    default: { font: default-font, fontColor: white }
},
com.badlogic.gdx.scenes.scene2d.ui.TextField$TextFieldStyle: {
    default: { selection: selection, background: textfield, font: default-font, fontColor: white, cursor: cursor }
},
com.badlogic.gdx.scenes.scene2d.ui.CheckBox$CheckBoxStyle: {
    default: { checkboxOn: check-on, checkboxOff: check-off, font: default-font, fontColor: white }
},
com.badlogic.gdx.scenes.scene2d.ui.List$ListStyle: {
    default: { fontColorUnselected: white, selection: default-rect-pad, fontColorSelected: white, font: default-font }
},
com.badlogic.gdx.scenes.scene2d.ui.Touchpad$TouchpadStyle: {
    default: { background: default-pane, knob: default-round-large }
},
com.badlogic.gdx.scenes.scene2d.ui.Tree$TreeStyle: {
    default: { minus: tree-minus, plus: tree-plus, selection: default-select-selection }
}
}

Update: I have updated my projects libgdx to latest(nightly build) and now I am getting different exception [com.badlogic.gdx.utils.GdxRuntimeException: Invalid line: ] and the exception detail is below.

Exception in thread "LWJGL Application" com.badlogic.gdx.utils.GdxRuntimeException: Error reading pack file: images/uiskin.atlas
    at com.badlogic.gdx.graphics.g2d.TextureAtlas$TextureAtlasData.<init>(TextureAtlas.java:178)
    at com.badlogic.gdx.graphics.g2d.TextureAtlas.<init>(TextureAtlas.java:222)
    at com.badlogic.gdx.graphics.g2d.TextureAtlas.<init>(TextureAtlas.java:217)
    at com.badlogic.gdx.graphics.g2d.TextureAtlas.<init>(TextureAtlas.java:207)
    at com.badlogic.gdx.graphics.g2d.TextureAtlas.<init>(TextureAtlas.java:202)
    at com.pactpub.libgdx.canyonbunny.screens.MenuScreen.rebuildStage(MenuScreen.java:72)
    at com.pactpub.libgdx.canyonbunny.screens.MenuScreen.show(MenuScreen.java:348)
    at com.badlogic.gdx.Game.setScreen(Game.java:61)
    at com.pactpub.libgdx.canyonbunny.CanyonBunnyMain.create(CanyonBunnyMain.java:15)
    at com.badlogic.gdx.backends.lwjgl.LwjglApplication.mainLoop(LwjglApplication.java:136)
    at com.badlogic.gdx.backends.lwjgl.LwjglApplication$1.run(LwjglApplication.java:114)
Caused by: com.badlogic.gdx.utils.GdxRuntimeException: Invalid line: <html class="   ">
    at com.badlogic.gdx.graphics.g2d.TextureAtlas.readValue(TextureAtlas.java:426)
    at com.badlogic.gdx.graphics.g2d.TextureAtlas$TextureAtlasData.<init>(TextureAtlas.java:111)

Answer 1

Taken from the latest uiskin.json from the tests.

com.badlogic.gdx.scenes.scene2d.ui.ScrollPane$ScrollPaneStyle: { default: { vScroll: default-scroll, hScrollKnob: default-round-large, background: default-rect, hScroll: default-scroll, vScrollKnob: default-round-large } },

Try to insert this in your uiskin.json and it might work. There have been several changes to the ScrollPane though and it might not work anymore with the old 0.9.9. You should consider using the latest version libgdx (nightly build).