Android WebView 上传文件支持全解析

默认情况下情况下，使用android的webview是不能够支持上传文件的。而这个，也是在我们的前端工程师告知之后才了解的。因为android的每个版本webview的实现有差异，因此需要对不同版本去适配。花了一点时间，参考别人的代码，这个问题已经解决，这里把我踩过的坑分享出来。
主要思路是重写webchromeclient，然后在webviewactivity中接收选择到的文件uri，传给页面去上传就可以了。
创建一个webviewactivity的内部类

public class xhswebchromeclient extends webchromeclient {

  // for android 3.0+
  public void openfilechooser(valuecallback<uri> uploadmsg) {
    clog.i("upfile", "in openfile uri callback");
    if (muploadmessage != null) {
      muploadmessage.onreceivevalue(null);
    }
    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 android 3.0+
  public void openfilechooser(valuecallback uploadmsg, string accepttype) {
    clog.i("upfile", "in openfile uri callback has accept type" + accepttype);
    if (muploadmessage != null) {
      muploadmessage.onreceivevalue(null);
    }
    muploadmessage = uploadmsg;
    intent i = new intent(intent.action_get_content);
    i.addcategory(intent.category_openable);
    string type = textutils.isempty(accepttype) ? "*/*" : accepttype;
    i.settype(type);
    startactivityforresult(intent.createchooser(i, "file chooser"),
        filechooser_resultcode);
  }

  // for android 4.1
  public void openfilechooser(valuecallback<uri> uploadmsg, string accepttype, string capture) {
    clog.i("upfile", "in openfile uri callback has accept type" + accepttype + "has capture" + capture);
    if (muploadmessage != null) {
      muploadmessage.onreceivevalue(null);
    }
    muploadmessage = uploadmsg;
    intent i = new intent(intent.action_get_content);
    i.addcategory(intent.category_openable);
    string type = textutils.isempty(accepttype) ? "*/*" : accepttype;
    i.settype(type);
    startactivityforresult(intent.createchooser(i, "file chooser"), filechooser_resultcode);
  }


//android 5.0+
  @override
  @suppresslint("newapi")
  public boolean onshowfilechooser(webview webview, valuecallback<uri[]> filepathcallback, filechooserparams filechooserparams) {
    if (muploadmessage != null) {
      muploadmessage.onreceivevalue(null);
    }
    clog.i("upfile", "file chooser params：" + filechooserparams.tostring());
    muploadmessage = filepathcallback;
    intent i = new intent(intent.action_get_content);
    i.addcategory(intent.category_openable);
    if (filechooserparams != null && filechooserparams.getaccepttypes() != null
        && filechooserparams.getaccepttypes().length > 0) {
      i.settype(filechooserparams.getaccepttypes()[0]);
    } else {
      i.settype("*/*");
    }
    startactivityforresult(intent.createchooser(i, "file chooser"), filechooser_resultcode);
    return true;
  }
}

上面openfilechooser是系统未暴露的接口，因此不需要加override的注解，同时不同版本有不同的参数，其中的参数，第一个valuecallback用于我们在选择完文件后，接收文件回调到网页内处理，accepttype为接受的文件mime type。在android 5.0之后，系统提供了onshowfilechooser来让我们实现选择文件的方法，仍然有valuecallback，在filechooserparams参数中，同样包括accepttype。我们可以根据accepttype，来打开系统的或者我们自己创建文件选择器。当然如果需要打开相机拍照，也可以自己去使用打开相机拍照的intent去打开即可。
处理选择的文件
以上是打开响应的选择文件的界面，我们还需要处理接收到文件之后，传给网页来响应。因为我们前面是使用startactivityforresult来打开的选择页面，我们会在onactivityresult中接收到选择的结果。show code：

@override
protected void onactivityresult(int requestcode, int resultcode, intent data) {
  super.onactivityresult(requestcode, resultcode, data);
  if (requestcode == filechooser_resultcode) {
    if (null == muploadmessage) return;
    uri result = data == null || resultcode != result_ok ? null : data.getdata();
    if (result == null) {
      muploadmessage.onreceivevalue(null);
      muploadmessage = null;
      return;
    }
    clog.i("upfile", "onactivityresult" + result.tostring());
    string path = fileutils.getpath(this, result);
    if (textutils.isempty(path)) {
      muploadmessage.onreceivevalue(null);
      muploadmessage = null;
      return;
    }
    uri uri = uri.fromfile(new file(path));
    clog.i("upfile", "onactivityresult after parser uri:" + uri.tostring());
    if (build.version.sdk_int >= build.version_codes.lollipop) {
      muploadmessage.onreceivevalue(new uri[]{uri});
    } else {
      muploadmessage.onreceivevalue(uri);
    }

    muploadmessage = null;
  }
}

以上代码主要就是调用valuecallback的onreceivevalue方法，将结果传回web。
注意，其他要说的，重要
由于不同版本的差别，android 5.0以下的版本，valuecallback 的onreceivevalue接收的参数类型是uri, 5.0及以上版本接收的是uri数组，在传值的时候需要注意。
选择文件会使用系统提供的组件或者其他支持的app，返回的uri有的直接是文件的url，有的是contentprovider的uri，因此我们需要统一处理一下，转成文件的uri，可参考以下代码（获取文件的路径）。
调用getpath可以将uri转成真实文件的path，然后可以自己生成文件的uri

public class fileutils {
  /**
   * @param uri the uri to check.
   * @return whether the uri authority is externalstorageprovider.
   */
  public static boolean isexternalstoragedocument(uri uri) {
    return "com.android.externalstorage.documents".equals(uri.getauthority());
  }

  /**
   * @param uri the uri to check.
   * @return whether the uri authority is downloadsprovider.
   */
  public static boolean isdownloadsdocument(uri uri) {
    return "com.android.providers.downloads.documents".equals(uri.getauthority());
  }

  /**
   * @param uri the uri to check.
   * @return whether the uri authority is mediaprovider.
   */
  public static boolean ismediadocument(uri uri) {
    return "com.android.providers.media.documents".equals(uri.getauthority());
  }

  /**
   * get the value of the data column for this uri. this is useful for
   * mediastore uris, and other file-based contentproviders.
   *
   * @param context the context.
   * @param uri the uri to query.
   * @param selection (optional) filter used in the query.
   * @param selectionargs (optional) selection arguments used in the query.
   * @return the value of the _data column, which is typically a file path.
   */
  public static string getdatacolumn(context context, uri uri, string selection,
                    string[] selectionargs) {

    cursor cursor = null;
    final string column = "_data";
    final string[] projection = {
        column
    };

    try {
      cursor = context.getcontentresolver().query(uri, projection, selection, selectionargs,
          null);
      if (cursor != null && cursor.movetofirst()) {
        final int column_index = cursor.getcolumnindexorthrow(column);
        return cursor.getstring(column_index);
      }
    } finally {
      if (cursor != null)
        cursor.close();
    }
    return null;
  }

  /**
   * get a file path from a uri. this will get the the path for storage access
   * framework documents, as well as the _data field for the mediastore and
   * other file-based contentproviders.
   *
   * @param context the context.
   * @param uri the uri to query.
   * @author paulburke
   */
  @suppresslint("newapi")
  public static string getpath(final context context, final uri uri) {

    final boolean iskitkat = build.version.sdk_int >= build.version_codes.kitkat;

    // documentprovider
    if (iskitkat && documentscontract.isdocumenturi(context, uri)) {
      // externalstorageprovider
      if (isexternalstoragedocument(uri)) {
        final string docid = documentscontract.getdocumentid(uri);
        final string[] split = docid.split(":");
        final string type = split[0];

        if ("primary".equalsignorecase(type)) {
          return environment.getexternalstoragedirectory() + "/" + split[1];
        }

        // todo handle non-primary volumes
      }
      // downloadsprovider
      else if (isdownloadsdocument(uri)) {

        final string id = documentscontract.getdocumentid(uri);
        final uri contenturi = contenturis.withappendedid(
            uri.parse("content://downloads/public_downloads"), long.valueof(id));

        return getdatacolumn(context, contenturi, null, null);
      }
      // mediaprovider
      else if (ismediadocument(uri)) {
        final string docid = documentscontract.getdocumentid(uri);
        final string[] split = docid.split(":");
        final string type = split[0];

        uri contenturi = null;
        if ("image".equals(type)) {
          contenturi = mediastore.images.media.external_content_uri;
        } else if ("video".equals(type)) {
          contenturi = mediastore.video.media.external_content_uri;
        } else if ("audio".equals(type)) {
          contenturi = mediastore.audio.media.external_content_uri;
        }

        final string selection = "_id=?";
        final string[] selectionargs = new string[] {
            split[1]
        };

        return getdatacolumn(context, contenturi, selection, selectionargs);
      }
    }
    // mediastore (and general)
    else if ("content".equalsignorecase(uri.getscheme())) {
      return getdatacolumn(context, uri, null, null);
    }
    // file
    else if ("file".equalsignorecase(uri.getscheme())) {
      return uri.getpath();
    }

    return null;
  }

}

再有，即使获取的结果为null，也要传给web，即直接调用muploadmessage.onreceivevalue(null),否则网页会阻塞。
最后，在打release包的时候，因为我们会混淆，要特别设置不要混淆webchromeclient子类里面的openfilechooser方法，由于不是继承的方法，所以默认会被混淆，然后就无法选择文件了。
就这样吧。
原文地址：

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持。