这并不是一个真正的问题，但是，我想在这里共享我的一些工作代码，以供您在需要时参考。

众所周知，HttpEntity自API22起已弃用该方法，并自API23起将其完全删除。目前，我们无法再在Android Developer上访问HttpEntity Reference（404）。因此，以下是我在带有Volley且没有HttpEntity的POST Multipart Request中工作的示例代码。工作正常，已通过测试Asp.Net Web API。当然，代码可能只是发布两个已存在的可绘制文件的基本示例，也不是所有情况下的最佳解决方案，并且调整也不佳。

MultipartActivity.java：

package com.example.multipartvolley;

import android.app.Activity;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.drawable.BitmapDrawable;
import android.graphics.drawable.Drawable;
import android.os.Bundle;
import android.support.v4.content.ContextCompat;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.Toast;

import com.android.volley.NetworkResponse;
import com.android.volley.Response;
import com.android.volley.VolleyError;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.DataOutputStream;
import java.io.IOException;


public class MultipartActivity extends Activity {

    private final Context context = this;
    private final String twoHyphens = "--";
    private final String lineEnd = "\r\n";
    private final String boundary = "apiclient-" + System.currentTimeMillis();
    private final String mimeType = "multipart/form-data;boundary=" + boundary;
    private byte[] multipartBody;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_multipart);

        byte[] fileData1 = getFileDataFromDrawable(context, R.drawable.ic_action_android);
        byte[] fileData2 = getFileDataFromDrawable(context, R.drawable.ic_action_book);

        ByteArrayOutputStream bos = new ByteArrayOutputStream();
        DataOutputStream dos = new DataOutputStream(bos);
        try {
            // the first file
            buildPart(dos, fileData1, "ic_action_android.png");
            // the second file
            buildPart(dos, fileData2, "ic_action_book.png");
            // send multipart form data necesssary after file data
            dos.writeBytes(twoHyphens + boundary + twoHyphens + lineEnd);
            // pass to multipart body
            multipartBody = bos.toByteArray();
        } catch (IOException e) {
            e.printStackTrace();
        }

        String url = "http://192.168.1.100/api/postfile";
        MultipartRequest multipartRequest = new MultipartRequest(url, null, mimeType, multipartBody, new Response.Listener<NetworkResponse>() {
            @Override
            public void onResponse(NetworkResponse response) {
                Toast.makeText(context, "Upload successfully!", Toast.LENGTH_SHORT).show();
            }
        }, new Response.ErrorListener() {
            @Override
            public void onErrorResponse(VolleyError error) {
                Toast.makeText(context, "Upload failed!\r\n" + error.toString(), Toast.LENGTH_SHORT).show();
            }
        });

        VolleySingleton.getInstance(context).addToRequestQueue(multipartRequest);
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_multipart, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }

    private void buildPart(DataOutputStream dataOutputStream, byte[] fileData, String fileName) throws IOException {
        dataOutputStream.writeBytes(twoHyphens + boundary + lineEnd);
        dataOutputStream.writeBytes("Content-Disposition: form-data; name=\"uploaded_file\"; filename=\""
                + fileName + "\"" + lineEnd);
        dataOutputStream.writeBytes(lineEnd);

        ByteArrayInputStream fileInputStream = new ByteArrayInputStream(fileData);
        int bytesAvailable = fileInputStream.available();

        int maxBufferSize = 1024 * 1024;
        int bufferSize = Math.min(bytesAvailable, maxBufferSize);
        byte[] buffer = new byte[bufferSize];

        // read file and write it into form...
        int bytesRead = fileInputStream.read(buffer, 0, bufferSize);

        while (bytesRead > 0) {
            dataOutputStream.write(buffer, 0, bufferSize);
            bytesAvailable = fileInputStream.available();
            bufferSize = Math.min(bytesAvailable, maxBufferSize);
            bytesRead = fileInputStream.read(buffer, 0, bufferSize);
        }

        dataOutputStream.writeBytes(lineEnd);
    }

    private byte[] getFileDataFromDrawable(Context context, int id) {
        Drawable drawable = ContextCompat.getDrawable(context, id);
        Bitmap bitmap = ((BitmapDrawable) drawable).getBitmap();
        ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
        bitmap.compress(Bitmap.CompressFormat.PNG, 0, byteArrayOutputStream);
        return byteArrayOutputStream.toByteArray();
    }
}

MultipartRequest.java：

package com.example.multipartvolley;

import com.android.volley.AuthFailureError;
import com.android.volley.NetworkResponse;
import com.android.volley.ParseError;
import com.android.volley.Request;
import com.android.volley.Response;
import com.android.volley.VolleyError;
import com.android.volley.toolbox.HttpHeaderParser;

import java.util.Map;

class MultipartRequest extends Request<NetworkResponse> {
    private final Response.Listener<NetworkResponse> mListener;
    private final Response.ErrorListener mErrorListener;
    private final Map<String, String> mHeaders;
    private final String mMimeType;
    private final byte[] mMultipartBody;

    public MultipartRequest(String url, Map<String, String> headers, String mimeType, byte[] multipartBody, Response.Listener<NetworkResponse> listener, Response.ErrorListener errorListener) {
        super(Method.POST, url, errorListener);
        this.mListener = listener;
        this.mErrorListener = errorListener;
        this.mHeaders = headers;
        this.mMimeType = mimeType;
        this.mMultipartBody = multipartBody;
    }

    @Override
    public Map<String, String> getHeaders() throws AuthFailureError {
        return (mHeaders != null) ? mHeaders : super.getHeaders();
    }

    @Override
    public String getBodyContentType() {
        return mMimeType;
    }

    @Override
    public byte[] getBody() throws AuthFailureError {
        return mMultipartBody;
    }

    @Override
    protected Response<NetworkResponse> parseNetworkResponse(NetworkResponse response) {
        try {
            return Response.success(
                    response,
                    HttpHeaderParser.parseCacheHeaders(response));
        } catch (Exception e) {
            return Response.error(new ParseError(e));
        }
    }

    @Override
    protected void deliverResponse(NetworkResponse response) {
        mListener.onResponse(response);
    }

    @Override
    public void deliverError(VolleyError error) {
        mErrorListener.onErrorResponse(error);
    }
}