我想替换的是 <image src="xxxx" />的地址

如果你想替换的是 `<img>` 标签中的 `src` 属性，那么你需要修改 JavaScript 代码中的正则表达式，以匹配 `<img>` 标签的 `src` 属性。下面是修改后的示例代码：

public class MyWebViewClient extends WebViewClient {
    @Override
    public void onPageFinished(WebView view, String url) {
        super.onPageFinished(view, url);
        String javascript = "javascript:(function() {"
                + "var imgs = document.getElementsByTagName('img');"
                + "for (var i = 0; i < imgs.length; i++) {"
                + "var img = imgs[i];"
                + "var url = img.getAttribute('src');"
                + "if (url.startsWith('http')) {"
                + "var xhr = new XMLHttpRequest();"
                + "xhr.open('GET', url, true);"
                + "xhr.responseType = 'arraybuffer';"
                + "xhr.onload = function() {"
                + "if (xhr.status === 200) {"
                + "var uInt8Array = new Uint8Array(xhr.response);"
                + "var i = uInt8Array.length;"
                + "var binaryString = new Array(i);"
                + "while (i--) {"
                + "binaryString[i] = String.fromCharCode(uInt8Array[i]);"
                + "}"
                + "var data = binaryString.join('');"
                + "var base64 = window.btoa(data);"
                + "img.setAttribute('src', 'data:image/png;base64,' + base64);"
                + "}"
                + "};"
                + "xhr.send();"
                + "}"
                + "}"
                + "})()";
        view.loadUrl(javascript);
    }
}

这段代码中，我们使用 `img.getAttribute('src')` 来获取 `<img>` 标签的 `src` 属性，然后将其替换为 Base64 编码字符串。同样，你需要将图片的本地路径替换为对应的路径。