PreloadConfig.fromJson constructor
从Map创建实例
json 包含预加载配置信息的Map对象
返回PreloadConfig实例
Implementation
factory PreloadConfig.fromJson(Map<String, dynamic> json) {
return PreloadConfig(
duration: json['duration'] as int? ?? 1000,
defaultResolution: json['defaultResolution'] as int?,
defaultBandWidth: json['defaultBandWidth'] as int?,
defaultQuality: json['defaultQuality'],
);
}