要解决安卓WebView中上传按钮无法工作的问题，可以尝试以下方法：

1. 添加文件选择器： 在你的WebViewClient中，重写onShowFileChooser()方法，并返回一个文件选择器。示例代码如下：

webView.setWebViewClient(new WebViewClient() {
    @Override
    public boolean onShowFileChooser(WebView webView, ValueCallback filePathCallback, WebChromeClient.FileChooserParams fileChooserParams) {
        // 创建一个选择文件的Intent
        Intent intent = fileChooserParams.createIntent();
        try {
            // 启动文件选择器
            startActivityForResult(intent, FILE_CHOOSER_RESULT_CODE);
        } catch (ActivityNotFoundException e) {
            e.printStackTrace();
            return false;
        }
        return true;
    }
});

2. 处理文件选择结果： 在你的Activity或Fragment中，重写onActivityResult()方法，并处理文件选择结果。示例代码如下：

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    super.onActivityResult(requestCode, resultCode, data);
    if (requestCode == FILE_CHOOSER_RESULT_CODE) {
        if (uploadMessage != null) {
            Uri[] results = null;
            if (resultCode == Activity.RESULT_OK) {
                if (data != null) {
                    // 获取选择的文件Uri
                    results = new Uri[] { data.getData() };
                }
            }
            // 将选择的文件Uri返回给WebView
            uploadMessage.onReceiveValue(results);
            uploadMessage = null;
        }
    }
}

3. 设置WebChromeClient： 在创建WebView时，为其设置WebChromeClient，并重写onShowFileChooser()方法和onActivityResult()方法。示例代码如下：

webView.setWebChromeClient(new WebChromeClient() {
    // For Android 3.0+
    public void openFileChooser(ValueCallback uploadMsg) {
        mUploadMessage = uploadMsg;
        // 创建一个选择文件的Intent
        Intent intent = new Intent(Intent.ACTION_GET_CONTENT);
        intent.addCategory(Intent.CATEGORY_OPENABLE);
        intent.setType("*/*");
        // 启动文件选择器
        startActivityForResult(Intent.createChooser(intent, "File Chooser"), FILE_CHOOSER_RESULT_CODE);
    }

    // For Android 3.0+
    public void openFileChooser(ValueCallback uploadMsg, String acceptType) {
        mUploadMessage = uploadMsg;
        // 创建一个选择文件的Intent
        Intent intent = new Intent(Intent.ACTION_GET_CONTENT);
        intent.addCategory(Intent.CATEGORY_OPENABLE);
        intent.setType(acceptType);
        // 启动文件选择器
        startActivityForResult(Intent.createChooser(intent, "File Chooser"), FILE_CHOOSER_RESULT_CODE);
    }

    // For Android < 3.0
    public void openFileChooser(ValueCallback uploadMsg, String acceptType, String capture) {
        mUploadMessage = uploadMsg;
        // 创建一个选择文件的Intent
        Intent intent = new Intent(Intent.ACTION_GET_CONTENT);
        intent.addCategory(Intent.CATEGORY_OPENABLE);
        intent.setType(acceptType);
        // 启动文件选择器
        startActivityForResult(Intent.createChooser(intent, "File Chooser"), FILE_CHOOSER_RESULT_CODE);
    }

    // For Android 5.0+
    @Override
    public boolean onShowFileChooser(WebView webView, ValueCallback filePathCallback, FileChooserParams fileChooserParams) {
        if (mUploadMessageArray != null) {
            mUploadMessageArray.onReceiveValue(null);
            mUploadMessageArray = null;
        }

        mUploadMessageArray = filePathCallback;
        // 创建一个选择文件的Intent
        Intent intent = fileChooserParams.createIntent();
        try {
            startActivityForResult(intent, FILE_CHOOSER_RESULT_CODE);
        } catch (ActivityNotFoundException e) {
            e.printStackTrace();
            mUploadMessageArray = null;
            return false;
        }
        return true;
    }
});

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    super.onActivityResult(requestCode, resultCode, data);
    if (requestCode == FILE_CHOOSER_RESULT_CODE) {
        if (mUploadMessage != null) {
            // For Android 3.0+
            Uri result = data == null || resultCode != RESULT_OK ? null : data.getData();
            mUploadMessage.onReceiveValue(result);
            mUploadMessage = null;
        } else if (mUploadMessageArray != null) {
            // For Android 5.0+
            Uri[] results = null;
            if (resultCode == Activity.RESULT_OK && data != null) {
                String dataString = data.getDataString();
                ClipData clipData = data.getClipData();
                if