loading fonts ttf crashes , error loading with libgdx : i have the problem with load the ttf file, my code: 

    Label migliaLabel;
    migliaLabel = new Label("label", new Label.LabelStyle(new BitmapFont(Gdx.files.internal("Kalam-Regular.ttf")), Color.MAGENTA));

the file Kalam-Regular.ttf is in the folder assets/Kalam-Regular.ttf
but when i run the game, android studio get in error: 

> FATAL EXCEPTION: GLThread 125
>                                                                                com.badlogic.gdx.utils.GdxRuntimeException: Error loading font file:
> Kalam-Regular.ttf
>                                                                                    at
> com.badlogic.gdx.graphics.g2d.BitmapFont$BitmapFontData.load(BitmapFont.java:665)
>                                                                                    at
> com.badlogic.gdx.graphics.g2d.BitmapFont$BitmapFontData.<init>(BitmapFont.java:475)
>                                                                                    at
> com.badlogic.gdx.graphics.g2d.BitmapFont.<init>(BitmapFont.java:114)
>                                                                                    at
> com.badlogic.gdx.graphics.g2d.BitmapFont.<init>(BitmapFont.java:107)
>                                                                                    at com.surfsurvivor.game.GameClass.show(GameClass.java:181)
>                                                                                    at com.badlogic.gdx.Game.setScreen(Game.java:61)
>                                                                                    at com.surfsurvivor.game.SurfClass.create(SurfClass.java:26)
>                                                                                    at
> com.badlogic.gdx.backends.android.AndroidGraphics.onSurfaceChanged(AndroidGraphics.java:254)
>                                                                                    at
> android.opengl.GLSurfaceView$GLThread.guardedRun(GLSurfaceView.java:1505)
>                                                                                    at android.opengl.GLSurfaceView$GLThread.run(GLSurfaceView.java:1240)
>                                                                                 Caused by: com.badlogic.gdx.utils.GdxRuntimeException: Invalid
> padding.
>                                                                                    at
> com.badlogic.gdx.graphics.g2d.BitmapFont$BitmapFontData.load(BitmapFont.java:488)
>                                                                                    at
> com.badlogic.gdx.graphics.g2d.BitmapFont$BitmapFontData.<init>(BitmapFont.java:475) 
>                                                                                    at
> com.badlogic.gdx.graphics.g2d.BitmapFont.<init>(BitmapFont.java:114) 
>                                                                                    at
> com.badlogic.gdx.graphics.g2d.BitmapFont.<init>(BitmapFont.java:107) 
>                                                                                    at com.surfsurvivor.game.GameClass.show(GameClass.java:181) 
>                                                                                    at com.badlogic.gdx.Game.setScreen(Game.java:61) 
>                                                                                    at com.surfsurvivor.game.SurfClass.create(SurfClass.java:26) 
>                                                                                    at
> com.badlogic.gdx.backends.android.AndroidGraphics.onSurfaceChanged(AndroidGraphics.java:254) 
>                                                                                    at
> android.opengl.GLSurfaceView$GLThread.guardedRun(GLSurfaceView.java:1505) 
>                                                                                    at android.opengl.GLSurfaceView$GLThread.run(GLSurfaceView.java:1240)

how can solve ? 
Thanks