h5页面中input type="file"的事件监听进行文件的上传如下图：

我们可以重写webview的webchromeClient中的openFileChooser方法，由于android系统有多个版本，因此需要重写多个openFileChooser进行兼容，而android5.0以后，需要重写onShowFileChooser方法，其上传的参数Uri变成了Uri[]类型，说明5.0以后支持多传图片。

public class WebViewActivity extends AppCompatActivity{ 
   private WebView webView;
   private WebSettings settings;
   private ValueCallback<Uri> uploadMessage;
   private ValueCallback<Uri[]> uploadMessageAboveL;
   private final static int FILE_CHOOSER_RESULT_CODE = 10000;

   @Override
   protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_web_view);
        webView = findViewById(R.id.webView);
        settings = webView.getSettings();
        settings.setJavaScriptEnabled(true);//支持JavaScript脚本
        webView.setWebChromeClient(new MyWebChromeClient());
        webView.setWebViewClient(new WebViewClient());
        webView.loadUrl("file:///android_asset/web.html");   
        }

      public class WebChromeClients extends WebChromeClient {
        // 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;
        }
    }


   private void openImageChooserActivity() {
        //调用自己的图库
        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) { //处理返回的图片，并进行上传
            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;
    }
}

重写该方法后就能实现上传功能：