Android 4.4 WebView selector de archivos no se abre?

Este Código funcionó para mí.

    private class MyWebChromeClient extends WebChromeClient {
    //The undocumented magic method override
    //Eclipse will swear at you if you try to put @Override here


    // For Android 3.0+
    public void openFileChooser(ValueCallback uploadMsg, String acceptType) {
        mUploadMessage = uploadMsg;
        Intent i = new Intent(Intent.ACTION_GET_CONTENT);
        i.addCategory(Intent.CATEGORY_OPENABLE);
        i.setType("*/*");
        MainActivity1.this.startActivityForResult(Intent.createChooser(i, "File Browser"), FILECHOOSER_RESULTCODE);
    }

    //For Android 4.1+ only
    protected void openFileChooser(ValueCallback<Uri> uploadMsg, String acceptType, String capture)
    {
        mUploadMessage = uploadMsg;
        Intent intent = new Intent(Intent.ACTION_GET_CONTENT);
        intent.addCategory(Intent.CATEGORY_OPENABLE);
        intent.setType("*/*");
        startActivityForResult(Intent.createChooser(intent, "File Browser"), FILECHOOSER_RESULTCODE);
    }

    protected void openFileChooser(ValueCallback<Uri> uploadMsg)
    {
        mUploadMessage = uploadMsg;
        Intent i = new Intent(Intent.ACTION_GET_CONTENT);
        i.addCategory(Intent.CATEGORY_OPENABLE);
        i.setType("*/*");
        startActivityForResult(Intent.createChooser(i, "File Chooser"), FILECHOOSER_RESULTCODE);
    }

    // For Lollipop 5.0+ Devices
    public boolean onShowFileChooser(WebView mWebView, ValueCallback<Uri[]> filePathCallback, WebChromeClient.FileChooserParams fileChooserParams) {
        if (uploadMessage != null) {
            uploadMessage.onReceiveValue(null);
            uploadMessage = null;
        }

        uploadMessage = filePathCallback;
        Intent intent = null;
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
            intent = fileChooserParams.createIntent();
        }
        try {
            startActivityForResult(intent, REQUEST_SELECT_FILE);
        } catch (ActivityNotFoundException e) {
            uploadMessage = null;
            Toast.makeText(getApplicationContext(), "Cannot Open File Chooser", Toast.LENGTH_LONG).show();
            return false;
        }
        return true;
    }

    @Override
    public boolean onJsAlert(WebView view, String url, String message, JsResult result) {

        Log.d("LogTag", message);
        result.confirm();
        return true;
    }
}

  @Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    if (requestCode == REQUEST_SELECT_FILE) {
        if (uploadMessage == null) return;
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
            uploadMessage.onReceiveValue(WebChromeClient.FileChooserParams.parseResult(resultCode, data));
        }
        uploadMessage = null;
    } else if (requestCode == FILECHOOSER_RESULTCODE) {
        if (null == mUploadMessage)
            return;
        // Use MainActivity.RESULT_OK if you're implementing WebView inside Fragment
        // Use RESULT_OK only if you're implementing WebView inside an Activity
        Uri result = data == null || resultCode != MainActivity.RESULT_OK ? null : data.getData();
        mUploadMessage.onReceiveValue(result);
        mUploadMessage = null;
    }
}

Estaba trabajando en este tema también, y el problema y aquí está mi solución

private class MyWebChromeClient extends WebChromeClient {


    /**
     * This is the method used by Android 5.0+ to upload files towards a web form in a Webview
     *
     * @param webView
     * @param filePathCallback
     * @param fileChooserParams
     * @return
     */
    @Override
    public boolean onShowFileChooser(
            WebView webView, ValueCallback<Uri[]> filePathCallback,
            WebChromeClient.FileChooserParams fileChooserParams) {

        if (mFilePathCallback != null) {
            mFilePathCallback.onReceiveValue(null);
        }
        mFilePathCallback = filePathCallback;

        Intent contentSelectionIntent = new Intent(Intent.ACTION_GET_CONTENT);
        contentSelectionIntent.addCategory(Intent.CATEGORY_OPENABLE);
        contentSelectionIntent.setType("image/*");

        Intent[] intentArray = getCameraIntent();

        Intent chooserIntent = new Intent(Intent.ACTION_CHOOSER);
        chooserIntent.putExtra(Intent.EXTRA_INTENT, contentSelectionIntent);
        chooserIntent.putExtra(Intent.EXTRA_TITLE, "Seleccionar Fuente");
        chooserIntent.putExtra(Intent.EXTRA_INITIAL_INTENTS, intentArray);

        startActivityForResult(chooserIntent, INPUT_FILE_REQUEST_CODE);

        return true;
    }

    @Override
    public void onProgressChanged(WebView view, int newProgress) {

        mProgressBar.setVisibility(View.VISIBLE);
        WebActivity.this.setValue(newProgress);
        super.onProgressChanged(view, newProgress);
    }

    @Override
    public boolean onJsAlert(WebView view, String url, String message, JsResult result) {

        Log.d("LogTag", message);
        result.confirm();
        return true;
    }

    /**
     * Despite that there is not a Override annotation, this method overrides the open file
     * chooser function present in Android 3.0+
     *
     * @param uploadMsg
     * @author Tito_Leiva
     */
    public void openFileChooser(ValueCallback<Uri> uploadMsg) {

        mUploadMessage = uploadMsg;
        Intent i = getChooserIntent(getCameraIntent(), getGalleryIntent("image/*"));
        i.addCategory(Intent.CATEGORY_OPENABLE);
        WebActivity.this.startActivityForResult(Intent.createChooser(i, "Selecciona la imagen"), FILECHOOSER_RESULTCODE);

    }

    public void openFileChooser(ValueCallback uploadMsg, String acceptType) {
        mUploadMessage = uploadMsg;
        Intent i = getChooserIntent(getCameraIntent(), getGalleryIntent("*/*"));
        i.addCategory(Intent.CATEGORY_OPENABLE);
        WebActivity.this.startActivityForResult(
                Intent.createChooser(i, "Selecciona la imagen"),
                FILECHOOSER_RESULTCODE);
    }

    /**
     * Despite that there is not a Override annotation, this method overrides the open file
     * chooser function present in Android 4.1+
     *
     * @param uploadMsg
     * @author Tito_Leiva
     */
    public void openFileChooser(ValueCallback<Uri> uploadMsg, String acceptType, String capture) {
        mUploadMessage = uploadMsg;
        Intent i = getChooserIntent(getCameraIntent(), getGalleryIntent("image/*"));
        WebActivity.this.startActivityForResult(Intent.createChooser(i, "Selecciona la imagen"), FILECHOOSER_RESULTCODE);

    }

    private Intent[] getCameraIntent() {

        // Determine Uri of camera image to save.
        Intent takePictureIntent = new Intent(WebActivity.this, CameraActivity.class);
        if (takePictureIntent.resolveActivity(getPackageManager()) != null) {
            // Create the File where the photo should go
            File photoFile = null;
            try {
                photoFile = createImageFile();
                takePictureIntent.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();
                takePictureIntent.putExtra(MediaStore.EXTRA_OUTPUT,
                        Uri.fromFile(photoFile));
            } else {
                takePictureIntent = null;
            }
        }

        Intent[] intentArray;
        if (takePictureIntent != null) {
            intentArray = new Intent[]{takePictureIntent};
        } else {
            intentArray = new Intent[0];
        }

        return intentArray;

    }

    private Intent getGalleryIntent(String type) {

        // Filesystem.
        final Intent galleryIntent = new Intent();
        galleryIntent.setType(type);
        galleryIntent.addCategory(Intent.CATEGORY_OPENABLE);
        galleryIntent.setAction(Intent.ACTION_GET_CONTENT);

        return galleryIntent;
    }

    private Intent getChooserIntent(Intent[] cameraIntents, Intent galleryIntent) {

        // Chooser of filesystem options.
        final Intent chooserIntent = Intent.createChooser(galleryIntent, "Seleccionar Fuente");

        // Add the camera options.
        chooserIntent.putExtra(Intent.EXTRA_INITIAL_INTENTS, cameraIntents);

        return chooserIntent;
    }
}

Un problema que resolví es que el uri entregado para el método onActivityResult() no tiene extensión. Para resolver esto utilizo este método

public static Uri savePicture(Context context, Bitmap bitmap, int maxSize) {

    int cropWidth = bitmap.getWidth();
    int cropHeight = bitmap.getHeight();

    if (cropWidth > maxSize) {
        cropHeight = cropHeight * maxSize / cropWidth;
        cropWidth = maxSize;

    }

    if (cropHeight > maxSize) {
        cropWidth = cropWidth * maxSize / cropHeight;
        cropHeight = maxSize;

    }

    bitmap = ThumbnailUtils.extractThumbnail(bitmap, cropWidth, cropHeight, ThumbnailUtils.OPTIONS_RECYCLE_INPUT);

    File mediaStorageDir = new File(
            Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES),
            context.getString(R.string.app_name)
    );

    if (!mediaStorageDir.exists()) {
        if (!mediaStorageDir.mkdirs()) {
            return null;
        }
    }

    String timeStamp = new SimpleDateFormat("yyyyMMdd_HHmmss").format(new Date());
    File mediaFile = new File(
            mediaStorageDir.getPath() + File.separator + "IMG_" + timeStamp + ".jpg"
    );

    // Saving the bitmap
    try {
        ByteArrayOutputStream out = new ByteArrayOutputStream();
        bitmap.compress(Bitmap.CompressFormat.JPEG, 80, out);

        FileOutputStream stream = new FileOutputStream(mediaFile);
        stream.write(out.toByteArray());
        stream.close();

    } catch (IOException exception) {
        exception.printStackTrace();
    }

    // Mediascanner need to scan for the image saved
    Intent mediaScannerIntent = new Intent(Intent.ACTION_MEDIA_SCANNER_SCAN_FILE);
    Uri fileContentUri = Uri.fromFile(mediaFile);
    mediaScannerIntent.setData(fileContentUri);
    context.sendBroadcast(mediaScannerIntent);

    return fileContentUri;
} 

Finalmente, onActivityResult() el método es

@Override
protected void onActivityResult(int requestCode, int resultCode,
                                Intent intent) {

    if (resultCode == RESULT_OK) {

        // This is for Android 4.4.4- (JellyBean & KitKat)
        if (requestCode == FILECHOOSER_RESULTCODE) {

            if (null == mUploadMessage) {
                super.onActivityResult(requestCode, resultCode, intent);
                return;
            }

            final boolean isCamera;

            if (intent == null) {
                isCamera = true;
            } else {
                final String action = intent.getAction();
                if (action == null) {
                    isCamera = false;
                } else {
                    isCamera = action.equals(android.provider.MediaStore.ACTION_IMAGE_CAPTURE);
                }
            }

            Uri selectedImageUri;

            if (isCamera) {

                selectedImageUri = mOutputFileUri;
                mUploadMessage.onReceiveValue(selectedImageUri);
                mUploadMessage = null;

                return;

            } else {

                try {

                    Bitmap bitmap = MediaStore.Images.Media.getBitmap(this.getContentResolver(), intent.getData());
                    selectedImageUri = intent == null ? null : ImageUtility.savePicture(this, bitmap, 1400);

                    mUploadMessage.onReceiveValue(selectedImageUri);
                    mUploadMessage = null;

                    return;

                } catch (IOException e) {
                    e.printStackTrace();
                }
            }

            // And this is for Android 5.0+ (Lollipop)
        } else if (requestCode == INPUT_FILE_REQUEST_CODE) {

            Uri[] results = null;

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

                    Bitmap bitmap = null;

                    try {
                        bitmap = MediaStore.Images.Media.getBitmap(this.getContentResolver(), intent.getData());
                    } catch (IOException e) {
                        e.printStackTrace();
                    }

                    Uri dataUri = ImageUtility.savePicture(this, bitmap, 1400);

                    if (dataUri != null) {
                        results = new Uri[]{dataUri};
                    }
                }
            }

            mFilePathCallback.onReceiveValue(results);
            mFilePathCallback = null;

            return;
        }
    } else {

        super.onActivityResult(requestCode, resultCode, intent);
        return;
    }
} 

Echa un vistazo esto. Debido a la api 19 4.4, webview se ha migrado para usar Chromium, no WebChromeClient.

Encontré una solución que funcionó para mí. He añadido una regla más en proguard-android.txt:

-keepclassmembers class * extends android.webkit.WebChromeClient {
     public void openFileChooser(...);
}

Lo que he hecho para solucionar este problema es implementar CrossWalk en mi proyecto. Sé que el tamaño de CrossWalk es significativo (agrega Chromium a su proyecto), pero realmente necesitaba esto para funcionar bien dentro de una aplicación nativa. Documenté cómo implementé esto aquí: http://maurizionapoleoni.de/blog/implementing-a-file-input-with-camera-support-in-android-with-crosswalk/

Necesita implementar una clase WebviewClient. Puede comprobar estos ejemplo .

webview.setWebViewClient(new myWebClient());

The web.setWebChromeClient(new WebChromeClient() {
//
}

Cree la clase llamada mywebClient y agregue el siguiente código para implementar la función onPageStarted(), la función shouldOvverideLoading() y la función onActivityresult() como se muestra a continuación.

public class myWebClient extends WebViewClient { 


     @Override
     public void onPageStarted(WebView view, String url, Bitmap favicon) { 
             super.onPageStarted(view, url, favicon);
     }

     @Override

     public boolean shouldOverrideUrlLoading(WebView view, String url) {       

        view.loadUrl(url);
       return true; 
     }

     @Override 
    public void onPageFinished(WebView view, String url) {   
        super.onPageFinished(view, url); 
    } 
 }

 //flipscreen not loading again

 @Override

 public void onConfigurationChanged(Configuration newConfig){  
       super.onConfigurationChanged(newConfig);

 } 

@Override 

protected void onActivityResult(int requestCode, int resultCode, Intent intent) { 

  if(requestCode==FILECHOOSER_RESULTCODE){
       if (null == mUploadMessage) return; Uri result = intent == null || resultCode != RESULT_OK ? null : intent.getData();    mUploadMessage.onReceiveValue(result); mUploadMessage = null; 

  } 

}

Descargar demo

He probado el Selector de archivos en una vista web utilizando la última versión de Android 4.4.3, y está funcionando bien. Supongo que Google ha solucionado el problema.