App.js

  loadAppResources = async () => {
    SplashScreen.hide();

    const fonts = [
      require("./assets/fonts/Roboto.ttf"),
      require("./assets/fonts/Roboto_bold.ttf"),
      require("./assets/fonts/Roboto_medium.ttf")
    ];

    const cachedFonts = fonts.map(font => {
      return Asset.loadAsync(font);
    });

    await Promise.all(cachedFonts);

    this.setState({ isAppReady: true });
  };