Android原生的WebView並不支援上傳檔案，需要我們自己實現相應的方法。於是我把工作中的相關程式碼記錄下來。下次直接拿來用就行了。一點一滴都是經驗。
1。需要定義三個變數

   private ValueCallback<Uri[]> uploadMessageAboveL;
    private final static int FILE_CHOOSER_RESULT_CODE = 10000;
    private ValueCallback<Uri> uploadMessage;

2.重寫Activity相關方法

    private void
 
 openImageChooserActivity() {
        Intent i = new Intent(Intent.ACTION_GET_CONTENT);
        i.addCategory(Intent.CATEGORY_OPENABLE);
        i.setType("image/*");
        startActivityForResult(Intent.createChooser(i, "Image Chooser"), FILE_CHOOSER_RESULT_CODE);
    }


    @Override
    protected
 
 void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        if (requestCode == FILE_CHOOSER_RESULT_CODE) {
            if (null == uploadMessage && null == uploadMessageAboveL) return;
            Uri result = data == null
 
 || resultCode != RESULT_OK ? null : data.getData();
            if (uploadMessageAboveL != null) {
                onActivityResultAboveL(requestCode, resultCode, data);
            } else if (uploadMessage != null) {
                uploadMessage.onReceiveValue(result);
                uploadMessage = null;
            }
        }
    }


    @TargetApi(Build.VERSION_CODES.LOLLIPOP)
    private void onActivityResultAboveL(int requestCode, int resultCode, Intent intent) {
        if (requestCode != FILE_CHOOSER_RESULT_CODE || uploadMessageAboveL == null)
            return;
        Uri[] results = null;
        if (resultCode == Activity.RESULT_OK) {
            if (intent != null) {
                String dataString = intent.getDataString();
                ClipData clipData = intent.getClipData();
                if (clipData != null) {
                    results = new Uri[clipData.getItemCount()];
                    for (int i = 0; i < clipData.getItemCount(); i++) {
                        ClipData.Item item = clipData.getItemAt(i);
                        results[i] = item.getUri();
                    }
                }
                if (dataString != null)
                    results = new Uri[]{Uri.parse(dataString)};
            }
        }
        uploadMessageAboveL.onReceiveValue(results);
        uploadMessageAboveL = null;
    }

3.重寫WebChromeClient中的相關方法

    // For Android < 3.0
        public void openFileChooser(ValueCallback<Uri> valueCallback) {
            uploadMessage = valueCallback;
            openImageChooserActivity();
        }

        // For Android  >= 3.0
        public void openFileChooser(ValueCallback valueCallback, String acceptType) {
            uploadMessage = valueCallback;
            openImageChooserActivity();
        }

        //For Android  >= 4.1
        public void openFileChooser(ValueCallback<Uri> valueCallback, String acceptType, String capture) {
            uploadMessage = valueCallback;
            openImageChooserActivity();
        }

        // For Android >= 5.0
        @Override
        public boolean onShowFileChooser(WebView webView, ValueCallback<Uri[]> filePathCallback, WebChromeClient.FileChooserParams fileChooserParams) {
            uploadMessageAboveL = filePathCallback;
            openImageChooserActivity();
            return true;
        }

大功告成，噢耶 <(￣︶￣)>