java - Using default skin with libgdx .. SerializationException: Error reading file: ui/uiskin.json -

i'm trying run desktop version of libgdx project, getting following error ..

exception in thread "lwjgl application" com.badlogic.gdx.utils.serializationexception: error reading file: ui/uiskin.json     @ com.badlogic.gdx.scenes.scene2d.ui.skin.load(skin.java:97)     @ com.badlogic.gdx.scenes.scene2d.ui.skin.<init>(skin.java:74)     @ com.mygdx.game.mainmenu.show(mainmenu.java:51)     @ com.badlogic.gdx.game.setscreen(game.java:61)     @ com.mygdx.game.splash$1.run(splash.java:48)     @ com.badlogic.gdx.scenes.scene2d.actions.runnableaction.run(runnableaction.java:42)     @ com.badlogic.gdx.scenes.scene2d.actions.runnableaction.act(runnableaction.java:32)     @ com.badlogic.gdx.scenes.scene2d.actions.sequenceaction.act(sequenceaction.java:65)     @ com.badlogic.gdx.scenes.scene2d.actor.act(actor.java:95)     @ com.badlogic.gdx.scenes.scene2d.group.act(group.java:49)     @ com.badlogic.gdx.scenes.scene2d.stage.act(stage.java:223)     @ com.badlogic.gdx.scenes.scene2d.stage.act(stage.java:186)     @ com.mygdx.game.splash.render(splash.java:29)     @ com.badlogic.gdx.game.render(game.java:46)     @ com.mygdx.game.colorcatch.render(colorcatch.java:19)     @ com.badlogic.gdx.backends.lwjgl.lwjglapplication.mainloop(lwjglapplication.java:215)     @ com.badlogic.gdx.backends.lwjgl.lwjglapplication$1.run(lwjglapplication.java:120) caused by: com.badlogic.gdx.utils.serializationexception: error reading file: ui/uiskin.json     @ com.badlogic.gdx.utils.json.fromjson(json.java:683)     @ com.badlogic.gdx.scenes.scene2d.ui.skin.load(skin.java:95)     ... 16 more caused by: com.badlogic.gdx.utils.serializationexception:      @ com.badlogic.gdx.scenes.scene2d.ui.skin$2.read(skin.java:416)     @ com.badlogic.gdx.scenes.scene2d.ui.skin$2.read(skin.java:410)     @ com.badlogic.gdx.utils.json.readvalue(json.java:867)     @ com.badlogic.gdx.scenes.scene2d.ui.skin$1.readvalue(skin.java:404)     @ com.badlogic.gdx.utils.json.fromjson(json.java:681)     ... 17 more caused by: com.badlogic.gdx.utils.reflect.reflectionexception: class not found: com.badlogic.gdx.scenes.scene2d.ui.tooltip$tooltipstyle     @ com.badlogic.gdx.utils.reflect.classreflection.forname(classreflection.java:30)     @ com.badlogic.gdx.scenes.scene2d.ui.skin$2.read(skin.java:414)     ... 21 more caused by: java.lang.classnotfoundexception: com.badlogic.gdx.scenes.scene2d.ui.tooltip$tooltipstyle     @ java.net.urlclassloader$1.run(urlclassloader.java:366)     @ java.net.urlclassloader$1.run(urlclassloader.java:355)     @ java.security.accesscontroller.doprivileged(native method)     @ java.net.urlclassloader.findclass(urlclassloader.java:354)     @ java.lang.classloader.loadclass(classloader.java:425)     @ sun.misc.launcher$appclassloader.loadclass(launcher.java:308)     @ java.lang.classloader.loadclass(classloader.java:358)     @ java.lang.class.forname0(native method)     @ java.lang.class.forname(class.java:191)     @ com.badlogic.gdx.utils.reflect.classreflection.forname(classreflection.java:28) 

project structure following ..

rob@work:~/git/test$ ls android       core     gradle             gradlew      ios   local.properties build.gradle  desktop  gradle.properties  gradlew.bat  libs  settings.gradle rob@work:~/git/test$ ls android/assets/ui/ default.fnt   uiskin.atlas   uiskin.json   uiskin.png 

simplified version of mainmenu ..

public class mainmenu implements screen {      private stage stage = new stage();     private textureatlas atlas;     private skin skin;     private button quit;      public mainmenu() {}      @override     public void render(float delta) {         gdx.gl.glclearcolor(0, 0, 0, 1);         gdx.gl.glclear(gl20.gl_color_buffer_bit);          stage.act(delta);         stage.draw();     }      @override     public void show() {          atlas = new textureatlas("ui/uiskin.atlas");         skin = new skin(gdx.files.internal("ui/uiskin.json"));         skin.addregions(atlas);     }      @override     public void resize(int width, int height) {          textbuttonstyle stylequit = new textbuttonstyle();         stylequit.up = skin.getdrawable("8layer");     } } 

did update libgdx version 1.6.4? tooltips ware added, if skin file missing them crash. check tests in libgdx repo see how looks like.