uni-app 真机上 previewImage 不显示 showToast 如何解决

uni-app 真机上 previewImage 不显示 showToast 如何解决 产品分类： uniapp/App

示例代码：

previewImg(current) {
let app = this;
uni.previewImage({
urls: app.imgList,
current: current,
success: function (res) {},
fail: function (res) {},
complete: function (res) {},
longPressActions: {
itemList: ["保存图片到本地"],
success: (data) => {
if (data.tapIndex == 0) {
let url = app.imgList[data.index];
uni.saveImageToPhotosAlbum({
filePath: url,
success: (res) => {
console.log(res);
app.$toast("保存成功！");
},
fail: (err) => {
console.log(err.errMsg);
},
});
}
},
fail: function (err) {
console.log(err.errMsg);
},
},
});
},