flutter与前端交互,利用in_app_web_view实现下载功能:
首先下载库,终端输入
flutter pub add flutter_inappwebview
之后导出
import 'package:flutter_inappwebview/flutter_inappwebview.dart';
即可使用。
创建in_app_web_view:
![](https://img-blog.csdnimg.cn/img_convert/dbfa0d91cefe3c0e230d97e9173b3efa.gif)
InAppWebView(
initialOptions:
InAppWebViewGroupOptions(
crossPlatform:InAppWebViewOptions(
useOnDownloadStart:true,
),
android: AndroidInAppWebViewOptions()
),
//老版本:initialUrl 新版本:initialUrlRequest
initialUrlRequest: URLRequest(
url: Uri.parse(widget.url),
)
)
![](https://img-blog.csdnimg.cn/img_convert/fb536b42c944d010eb0131930569c9e7.gif)
因为要下载文件,所以请务必手动设置 useOnDownloadStart 为 true(否则出发文件下载的监听)。
initialUrlRequest中可填写自己想首先打开的url地址。
可参考例子:flutter_inappwebview_examples/main.dart at main · pichillilorenzo/flutter_inappwebview_examples · GitHub
https://github.com/pichillilorenzo/flutter_inappwebview_examples/blob/main/file_download/lib/main.dart
填写自己需要的回调(例子中的一点错误,没有开启 useOnDownloadStart, 因此不会下载成功,在使用时请设置为true)
正常情况下,配合downloader和android_path_provider,普通https链接即可下载文件。
而遇到blob链接时,还需要进行更多操作来确保文件的下载:
可参考javascript - Flutter WebView blob pdf download - Stack Overflow
https://stackoverflow.com/questions/64865972/flutter-webview-blob-pdf-download/64902313#64902313
因为Android不支持blob链接下载,因此我们嵌套javascript处理下载链接,在in_app_web_view的build中重写onWebViewCreated方法,添加javascriptHandler:
![](https://img-blog.csdnimg.cn/img_convert/781e0c85cd521e9e43d2f645cc2dc326.gif)
onWebViewCreated: (InAppWebViewController controller) {
if (mounted) {
setState(() {
_inAppWebCtrl = controller;
_inAppWebCtrl!.addJavaScriptHandler(
handlerName: 'blobToBase64Handler',
callback: (data) async {
if (data.isNotEmpty) {
final String receivedFileInBase64 = data[0];
final String receivedMimeType = data[1];
// NOTE: create a method that will handle your extensions
final String extension =
_mapMimeTypeToExtension(receivedMimeType);
String tmpFileName = 'tmpfile';
_createFileFromBase64(
receivedFileInBase64, tmpFileName, extension);
}
},
);
});
}
},
![](https://img-blog.csdnimg.cn/img_convert/66a0fe0b1bf82b14e8e484e771f8755c.gif)
首先在assets中添加js文件夹,然后创建 base64.js 文件
![](https://img-blog.csdnimg.cn/img_convert/6e2b6eaed84b38abf4f204339cb06c8a.gif)
var xhr = new XMLHttpRequest();
var blobUrl = "blobUrlPlaceholder";
console.log(blobUrl);
xhr.open('GET', blobUrl, true);
xhr.responseType = 'blob';
xhr.onload = function(e) {
if (this.status == 200) {
var blob = this.response;
var reader = new FileReader();
reader.readAsDataURL(blob);
reader.onloadend = function() {
var base64data = reader.result;
var base64ContentArray = base64data.split(",");
var mimeType = base64ContentArray[0].match(/[^:\s*]\w+\/[\w-+\d.]+(?=[;| ])/)[0];
var decodedFile = base64ContentArray[1];
console.log(mimeType);
window.flutter_inappwebview.callHandler('blobToBase64Handler', decodedFile, mimeType);
};
};
};
xhr.send();
![](https://img-blog.csdnimg.cn/img_convert/abf4c80c17e9666e9bc4233de31f906b.gif)
注意js中的callhander的名字参数,对应创建webview时addJavascriptHandler中的name。
另外是文件类型映射函数和文件下载函数:
![](https://img-blog.csdnimg.cn/img_convert/944311905ec5b8ecb50bb63f552ee094.gif)
String _mapMimeTypeToExtension(String mimeType) {
String extension = '';
switch(mimeType) {
case 'image/png': extension = 'png'; break;
case 'application/msword': extension = 'doc'; break;
case 'application/vnd.openxmlformats-officedocument.wordprocessingml.document':
extension = 'docx';
break;
case 'image/jpeg': extension = 'jpg'; break;
case 'image/gif': extension = 'gif'; break;
case 'image/svg+xml': extension = 'svg'; break;
case 'image/tiff': extension = 'tif'; break;
case 'text/plain': extension = 'txt'; break;
case 'application/vnd.ms-powerpoint': extension = 'ppt'; break;
case 'application/vnd.openxmlformats-officedocument.presentationml.presentation':
extension = 'pptx';
break;
case 'application/vnd.ms-excel': extension = 'xls'; break;
case 'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet':
extension = 'xlsx';
break;
case 'application/zip': extension = 'zip'; break;
case 'application/x-7z-compressed': extension = '7z'; break;
case 'application/pdf': extension = 'pdf'; break;
}
return extension;
}
_createFileFromBase64(String base64content, String fileName, String yourExtension) async {
var bytes = base64Decode(base64content.replaceAll('\n', ''));
final file = File("$_localPath/$fileName.$yourExtension");
await file.writeAsBytes(bytes.buffer.asUint8List());
}
![](https://img-blog.csdnimg.cn/img_convert/9147e4f99b942498a1a354a88017df9f.gif)
最后重写inappwebview中的下载请求方法:
![](https://img-blog.csdnimg.cn/img_convert/6c66429bce5718bfc611db87cc69fa88.gif)
onDownloadStartRequest: (controller, downloadStartRequest) async {
var jsContent = await rootBundle.loadString("assets/js/base64.js");
// 运行javascript代码解析blob
await controller.evaluateJavascript(
source: jsContent.replaceAll("blobUrlPlaceholder",
downloadStartRequest.url.toString()));
},
![](https://img-blog.csdnimg.cn/img_convert/944311905ec5b8ecb50bb63f552ee094.gif)
总结:因为android本身不能解析blob,我们因此使用javascript作为翻译:运行顺序:
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