uniapp更改导航栏按钮文字

//pages.json中
{
			"path": "pages/shopCart/shopCart",
			"style": {
				"navigationBarTitleText": "购物车",
				"app-plus": {
					"titleNView": {
						"buttons": [{
							// #ifdef APP-PLUS
							"text": "编辑",
							// #endif
							"fontSize": "16",
							"color": "#b6b6b6",
							"width": 70
						}],
						"splitLine": {//导航栏下划线
							"color": "#F4f4f4",
							"height": "1px"
						}
					}
				}
			}
		},
//导航栏按钮事件
onNavigationBarButtonTap(e) {
		var index = e.index;
		// 按钮文字的改变所需
		// #ifdef APP-PLUS
		var currentWebview = this.$mp.page.$getAppWebview();
		var tn = currentWebview.getStyle().titleNView;
		console.log(tn);
		var text = tn.buttons[0].text;
		console.log(text);
		if (text == '编辑') {
			this.cartStatus = true;
			tn.buttons[0].text = '完成';
			currentWebview.setStyle({
				titleNView: tn
			});
		} else if (text == '完成') {
			this.cartStatus = false;
			tn.buttons[0].text = '编辑';
			currentWebview.setStyle({
				titleNView: tn
			});
		}
		// #endif
	},