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[webview_flutter] Add interface methods to load local files and HTML strings. #4446

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Nov 4, 2021
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[webview_flutter] Add interface methods to load local files and HTML strings. #4446

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4b7a63f
Add methods to load HTML and Flutter assets.
mvanbeusekom Oct 22, 2021
3151008
Renamed loadHtml to loadHtmlString
mvanbeusekom Oct 27, 2021
0f28905
Support loading arbitrary files instead of only Flutter assets
mvanbeusekom Oct 27, 2021
7a0c69a
Update changelog description
mvanbeusekom Oct 27, 2021
c126eb6
Merge branch 'master' into feature/webview_load_asset
mvanbeusekom Oct 29, 2021
7a59328
Rebase with master
mvanbeusekom Nov 4, 2021
b2efaa8
Fix formatting
mvanbeusekom Nov 4, 2021
0f70b11
Fix formatting
mvanbeusekom Nov 4, 2021
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4 changes: 4 additions & 0 deletions packages/webview_flutter/webview_flutter_platform_interface/CHANGELOG.md
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@@ -1,3 +1,7 @@
## 1.3.0

* Added `loadFlutterAsset` and `loadHtml` interface methods.
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## 1.2.0

* Added `runJavascript` and `runJavascriptReturningResult` interface methods to supersede `evaluateJavascript`.
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18 changes: 18 additions & 0 deletions ...ter/webview_flutter_platform_interface/lib/src/method_channel/webview_method_channel.dart
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Expand Up @@ -79,6 +79,24 @@ class MethodChannelWebViewPlatform implements WebViewPlatformController {
);
}

@override
Future<void> loadFlutterAsset(String assetName) async {
assert(assetName != null);
return _channel.invokeMethod<void>('loadFlutterAsset', assetName);
}
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You've listed issues for both assets and arbitrary local files in the PR description; why are we restricting to assets here?

It's not clear to me that we should actually support assets on a per-plugin basis, in fact, since there are other cases where someone may want asset paths (e.g., FFI). It might make more sense to just support file paths, and then have a dedicated plugin (or maybe a function in path_provider) to get asset paths.

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As far as I know, it is not possible to load files in the WKWebView control that live outside the application bundle (due to security reasons). By only allowing loading of Flutter assets you force developers to add their HTML files as part of the iOS bundle ensuring that the file is always available and can be loaded.

This might be a bit restrictive to other platforms however I think it will cover most use cases where people wish to load local files. At least that was my reasoning.

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As far as I know, it is not possible to load files in the WKWebView control that live outside the application bundle (due to security reasons).

Do you have a source for that? It's not a documented restriction of the file-loading API.

This might be a bit restrictive to other platforms however I think it will cover most use cases where people wish to load local files. At least that was my reasoning.

One of the issues you linked is explicitly about a use case where assets wouldn't work; I don't think we have any data on how common one or the other use case is.

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No I don't have any documentation to back that up. And there are indeed samples that allow you to load information from for example the Documents directory. My bad.

I will update the interface to accept an absolute file path instead.

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@mvanbeusekom mvanbeusekom Oct 27, 2021 •
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Done. I those to accept only the absolute file path as that seems to be the easiest way to work cross platform.

On Android the WebView.loadUrl method requires the path to be prefixed with file:// (which we can take care of internally).

The [WKWebView loadFileURL:] only accepts an instance of the NSURL class which can easily be created from the absolute path using the [NSURL fileURLWithPath:] method.


@override
Future<void> loadHtml(
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How about loadHtmlString; we expect all of the mechanism for loading to provide HTML so this seems confusingly vague.

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Renamed.

String html, {
String? baseUrl,
}) async {
assert(html != null);
return _channel.invokeMethod<void>('loadHtml', <String, dynamic>{
'html': html,
'baseUrl': baseUrl,
});
}

@override
Future<void> loadUrl(
String url,
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23 changes: 23 additions & 0 deletions ...ew_flutter_platform_interface/lib/src/platform_interface/webview_platform_controller.dart
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Expand Up @@ -23,6 +23,29 @@ abstract class WebViewPlatformController {
/// The `handler` parameter must not be null.
WebViewPlatformController(WebViewPlatformCallbacksHandler handler);

/// Loads the Flutter asset specified in the pubspec.yaml file.
///
/// Throws an ArgumentError if [assetName] is not part of the specified assets
/// in the pubspec.yaml file.
Future<void> loadFlutterAsset(
String assetName,
) {
throw UnimplementedError(
"WebView loadFlutterAsset is not implemented on the current platform");
}

/// Loads the supplied HTML.
///
/// The [baseUrl] parameter is used when resolving relative URLs within the
/// HTML string.
Future<void> loadHtml(
String html, {
String? baseUrl,
}) {
throw UnimplementedError(
"WebView loadHtml is not implemented on the current platform");
}

/// Loads the specified URL.
///
/// If `headers` is not null and the URL is an HTTP URL, the key value paris in `headers` will
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2 changes: 1 addition & 1 deletion packages/webview_flutter/webview_flutter_platform_interface/pubspec.yaml
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Expand Up @@ -4,7 +4,7 @@ repository: https://github.com/flutter/plugins/tree/master/packages/webview_flut
issue_tracker: https://github.com/flutter/flutter/issues?q=is%3Aissue+is%3Aopen+label%3A%22p%3A+webview_flutter%22
# NOTE: We strongly prefer non-breaking changes, even at the expense of a
# less-clean API. See https://flutter.dev/go/platform-interface-breaking-changes
version: 1.2.0
version: 1.3.0

environment:
sdk: ">=2.12.0 <3.0.0"
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55 changes: 55 additions & 0 deletions ...bview_flutter_platform_interface/test/src/method_channel/webview_method_channel_test.dart
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Expand Up @@ -55,6 +55,61 @@ void main() {
log.clear();
});

test('loadFlutterAsset', () async {
await webViewPlatform.loadFlutterAsset(
'folder/asset.html',
);

expect(
log,
<Matcher>[
isMethodCall(
'loadFlutterAsset',
arguments: 'folder/asset.html',
),
],
);
});

test('loadHtml without base URL', () async {
await webViewPlatform.loadHtml(
'Test HTML string',
);

expect(
log,
<Matcher>[
isMethodCall(
'loadHtml',
arguments: <String, String?>{
'html': 'Test HTML string',
'baseUrl': null,
},
),
],
);
});

test('loadHtml without base URL', () async {
await webViewPlatform.loadHtml(
'Test HTML string',
baseUrl: 'https://flutter.dev',
);

expect(
log,
<Matcher>[
isMethodCall(
'loadHtml',
arguments: <String, String?>{
'html': 'Test HTML string',
'baseUrl': 'https://flutter.dev',
},
),
],
);
});

test('loadUrl with headers', () async {
await webViewPlatform.loadUrl(
'https://test.url',
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