这个问题的解决方法是在onActivityResult方法中使用手动触发的onShowFileChooser回调。解决步骤如下：

1. 确保你添加了以下两个权限：

2. 添加以下代码到WebChromeClient的onShowFileChooser:

   ValueCallback mUploadMessage; String mCameraPhotoPath;

   public boolean onShowFileChooser(WebView webView, ValueCallback filePathCallback, WebChromeClient.FileChooserParams fileChooserParams) { // Ensure that there's no existing callback if (mUploadMessage != null) { mUploadMessage.onReceiveValue(null); } mUploadMessage = filePathCallback;

    // Create camera intent
    Intent cameraIntent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
    if (cameraIntent.resolveActivity(getActivity().getPackageManager()) != null) {
        // Create a file to store the image
        File photoFile = null;
        try {
            photoFile = createImageFile();
            cameraIntent.putExtra("PhotoPath", mCameraPhotoPath);
        } catch (IOException ex) {
            // Error occurred while creating the File
            Log.e(TAG, "Unable to create Image File", ex);
        }
   
        // Continue only if the File was successfully created
        if (photoFile != null) {
            mCameraPhotoPath = "file:" + photoFile.getAbsolutePath();
            cameraIntent.putExtra(MediaStore.EXTRA_OUTPUT, Uri.fromFile(photoFile));
        } else {
            cameraIntent = null;
        }
    }
   
    // Create file chooser intent
    Intent intent = new Intent(Intent.ACTION_GET_CONTENT);
    intent.addCategory(Intent.CATEGORY_OPENABLE);
    intent.setType("*/*");
   
    // Create file chooser intent
    Intent chooserIntent = Intent.createChooser(intent, "选择文件");
   
    // Add the camera options
    if (cameraIntent != null) {
        chooserIntent.putExtra(Intent.EXTRA_INITIAL_INTENTS, new Intent[] { cameraIntent });
    }
   
    // Launch the file chooser
    startActivityForResult(chooserIntent, INPUT_FILE_REQUEST_CODE);
    return true;
   

   }

3. 添加以下代码到Activity的onActivityResult:

   @Override public void onActivityResult (int requestCode, int resultCode, Intent data) { if (requestCode != INPUT_FILE_REQUEST_CODE || mUploadMessage == null) { super.onActivityResult(requestCode, resultCode, data); return; }

    Uri[] results = null;
   
    // Check that the response is a good one
    if (resultCode == Activity.RESULT_OK) {
        if (data == null) {
            // If there is not data, then we may have taken a photo
            if (mCameraPhotoPath != null) {
                results = new Uri[] { Uri.parse(mCameraPhotoPath) };
            }
        } else {
            String dataString = data.getDataString();
            if (dataString != null) {
                results = new Uri[] { Uri.parse(dataString) };
            }
        }
    }
   
    mUploadMessage.onReceiveValue(results);
    mUploadMessage = null;
   

   }

4. 最后，定义输入文件请求代码。

   private static final int INPUT_FILE_REQUEST_CODE = 1;

通过这些步骤，您可以成功处理Android WebView onShowFileChooser方法无法显示结果的问题。