title: libdgx how to set style of TextButton?
body: <p>Using the <a href="https://github.com/libgdx/libgdx/blob/master/tests/gdx-tests-android/assets/data/uiskin.json" rel="nofollow" title="uiskin.json">uiskin.json</a> by default </p>
  
  <p>It contains</p>
  
  <pre><code>com.badlogic.gdx.scenes.scene2d.ui.Label$LabelStyle: {
  default: { font: default-font, fontColor: white }
  },
  com.badlogic.gdx.scenes.scene2d.ui.TextButton$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 }
  },
  </code></pre>
  
  <p>--</p>
  
  <pre><code>skin = new Skin(Gdx.files.internal("data/uiskin.json"));
  TextButton button = new TextButton("my button",skin);
  </code></pre>
  
  <p>if clicked, it will change color using <code>button.setColor(Color.RED);</code> This works well.</p>
  
  <p>if clicked again, I want it to change back to the default style. I wrote the following but it causes an error</p>
  
  <pre><code>button.setStyle(new TextButton.TextButtonStyle());
  </code></pre>
  
  <p>The error is:</p>
  
  <pre><code>FATAL EXCEPTION GLThread 2812
  java.lang.IllegalRuntimeException: Missing LabelStyleFont
  </code></pre>
  
  <p>I have the files default.fnt and default.png in my assets folder already. Please enlighten me!</p>