微信小程序保存图片（长按保存and点击保存）

一、长按图片保存

只需要image标签给上‘ show-menu-by-longpress=‘1’’属性，就可以实现长按保存功能及长按识别图片中小程序二维码，特别方便

<image src="1.png" show-menu-by-longpress='1'></image>

二、点击按钮保存图片至相册

如果调取用户授权访问相册，在用户拒绝后，安卓会出现无法再继续保存的问题，这边给出苹果和安卓都适用的方法，代码如下：

<button bindtap="savePoster">     保存到相册  </button >

savePoster() {
    const that = this    let fileName = new Date().valueOf(); let filePath = wx.env.USER_DATA_PATH + '/' + fileName + '.jpg'
    //这边就是为了安卓做的兼容，因为安卓机有可能会将图片地址的后缀名读取为：unknow   
    wx.downloadFile({
        url: that.data.imgUrl,
        //需要保存的图片地址     
        filePath: filePath,
        success: function (res) {
            // 保存图片到系统相册       
            wx.saveImageToPhotosAlbum({
                filePath: filePath,
                success(data) {
                    let fileMgr = wx.getFileSystemManager()
                    fileMgr.unlink({
                        filePath: filePath, success() {
                            wx.showToast({
                                title: '已保存至您的相册', icon: 'none',
                                duration: 1500
                            });
                        }
                    })
                }, fail(err) {
                    if (err.errMsg === "saveImageToPhotosAlbum:fail:auth denied" || err.errMsg === "saveImageToPhotosAlbum:fail auth deny" || err.errMsg === "saveImageToPhotosAlbum:fail authorize no response") { wx.showModal({ title: '提示', content: '需要您授权保存相册', showCancel: false, success: modalSuccess => { wx.openSetting({ success(settingdata) { if (settingdata.authSetting['scope.writePhotosAlbum']) { console.log('获取权限成功，给出再次点击图片保存到相册的提示。') } else { console.log('获取权限失败，给出不给权限就无法正常使用的提示') } } }) } }) }
                }
            })
        }, fail: function (res) { }
    })
},

如果要调微信授权的保存相册，可以用以下代码：

// 保存海报到相册  
savePoster() {
    let that = this
    wx.getSetting({
        success(res) {
            if (res.authSetting['scope.writePhotosAlbum']) {
                that.saveImg();
            } else if (res.authSetting['scope.writePhotosAlbum'] === undefined) {
                wx.authorize({
                    scope: 'scope.writePhotosAlbum',
                    success() { that.saveImg(); },
                    fail() {
                        that.authConfirm()
                    }
                })
            } else { that.authConfirm() }
        }
    })
},
// 授权拒绝后，再次授权提示弹窗 
authConfirm() {
    let that = this
    wx.showModal({
        content: '检测到您没打开保存图片权限，是否去设置打开？',
        confirmText: "确认", cancelText: "取消",
        success: function (res) {
            if (res.confirm) {
                wx.openSetting({
                    success(res) {
                        if (res.authSetting['scope.writePhotosAlbum']) {
                            that.saveImg();
                        } else { wx.showToast({ title: '您没有授权，无法保存到相册', icon: 'none' }) }
                    }
                })
            } else { wx.showToast({ title: '您没有授权，无法保存到相册', icon: 'none' }) }
        }
    });
},
//保存图片 
saveImg: function () {
    var that = this; var imgUrl = that.data.imgUrl;
    //需要保存的图片地址  
    console.log(imgUrl)
    wx.downloadFile({
        url: imgUrl, success(res) {
            // 只要服务器有响应数据，就会把响应内容写入文件并进入 success 回调，业务需要自行判断是否下载到了想要的内容   
            console.log('downloadFileres', res);
            wx.saveImageToPhotosAlbum({
                filePath: res.tempFilePath, success(res) {
                    console.log("保存图片：success");
                    wx.showToast({ title: '保存成功', });
                },
                fail: res => {
                    console.log(res); wx.showToast({
                        title: '保存失败',
                    });
                }
            })
        }
    })
}