在pages.json文件的第14行后面一行插入"navigationStyle": "custom"就可以取消APP的边框（顶部导航栏） 改后的完整代码如下

{
	"pages": [ //pages数组中第一项表示应用启动页，参考：https://uniapp.dcloud.io/collocation/pages
		{
			"path": "pages/index/index",
			"style": {
				"navigationBarTitleText": "mwapp"
			}
		}
	],
	"globalStyle": {
		"navigationBarTextStyle": "black",
		"navigationBarTitleText": "uni-app",
		"navigationBarBackgroundColor": "#00000000",
		"backgroundColor": "#00000000",
		"navigationStyle": "custom"
	},
	"uniIdRouter": {}
}