在Xamarin.Froms中创建WebView扩展以显示gif.我无法在Android上加载图像

本文介绍了在Xamarin.Froms中创建WebView扩展以显示gif.我无法在Android上加载图像的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！

问题描述

iOS可以正常工作.我也尝试过将.gif添加到资产文件夹(将BaseUrl设置为"file:///android_asset")也没有运气.有什么想法吗?

iOS works as expected. I have tried adding the .gif to the assets folder too (setting the BaseUrl to "file:///android_asset") with no luck. Any ideas?

imageHtml = "<center><body bgcolor =\""
                        + GetBackgroundColorHex()
                        + "\""
                        + heightAndWidth
                        + ">"
                        + (!string.IsNullOrWhiteSpace(imageFileName)
                            ? "<img src=\""
                            + imageFileName
                            + "\""
                            + heightAndWidth
                            + "/>"
                            : "&nbsp;")
                        + "</body></center>";

            HtmlWebViewSource source = new HtmlWebViewSource()
            {
                Html = imageHtml
            };

            if (Device.RuntimePlatform == Device.Android && !string.IsNullOrWhiteSpace(imageFileName))
            {
                source.BaseUrl = "file:///android_res/drawable/";
            }

            Source = source;

这是我在输出中得到的错误:

Here's the error I get in output:

12-11 02:08:00.256 E/AndroidProtocolHandler(12895): Unable to open resource URL: file:///android_res/drawable/Loading.gif
12-11 02:08:00.256 E/AndroidProtocolHandler(12895): java.lang.NoSuchFieldException: Loading
12-11 02:08:00.256 E/AndroidProtocolHandler(12895):     at java.lang.Class.getField(Class.java:1549)
12-11 02:08:00.256 E/AndroidProtocolHandler(12895):     at org.chromium.android_webview.AndroidProtocolHandler.getFieldId(AndroidProtocolHandler.java:40)
12-11 02:08:00.256 E/AndroidProtocolHandler(12895):     at org.chromium.android_webview.AndroidProtocolHandler.openResource(AndroidProtocolHandler.java:54)
12-11 02:08:00.256 E/AndroidProtocolHandler(12895):     at org.chromium.android_webview.AndroidProtocolHandler.open(AndroidProtocolHandler.java:10)

推荐答案

您可以通过资产而不是可绘制对象加载Android.Webkit.WebView内容.

You can load Android.Webkit.WebView content via assets, not drawables.

这是Xamarin.Android代码，用于分析图像以获取其宽度/高度，以确保保留宽高比，并从Asset文件夹中显示该图像:

Here is the Xamarin.Android code to parse the image to get its width/height to insure the aspect ratio is preserved and display it from the Asset folder:

var src = "out.gif";
var backgroundColor = "#ff0000";
int imageWidth;
int imageHeight;
using (var stream = Assets.Open(src))
using (var options = new BitmapFactory.Options { InJustDecodeBounds = true })
{
    await BitmapFactory.DecodeStreamAsync(stream, null, options);
    imageWidth = options.OutWidth;
    imageHeight = options.OutHeight;
}
var html = $"<body bgcolor={backgroundColor};\"><img src=\"{src}\" alt=\"A Gif file\" width=\"{imageWidth}\" height=\"{imageHeight}\" style=\"width: 100%; height: auto;\"/></body>";
webView.Settings.AllowFileAccessFromFileURLs = true;
webView.LoadDataWithBaseURL("file:///android_asset/", html, "text/html", "UTF-8", "");

var src = "image.gif";
var backgroundColor = "#ff0000";
int imageWidth = 300;
int imageHeight = 200;
var html = $"<body bgcolor={backgroundColor};\"><img src=\"{src}\" alt=\"A Gif file\" width=\"{imageWidth}\" height=\"{imageHeight}\" style=\"width: 100%; height: auto;\"/></body>";
webView.Source = new HtmlWebViewSource
{
    Html = html
};

注意:image.gif位于Android资产(AndroidResource)文件夹和iOS资源文件夹(BundleResource)

Note: image.gif is in the Android Assets (AndroidResource) folder and iOS Resource folder (BundleResource)

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