个人开发日志

OKHTTP3 简单使用(四) 上传文件

文件上传基于POST，因此和POST写法基本一致，但是不再使用FormBody，FormBody使用的MideaType(Content-Type)为"application/x-www-form-urlencoded; charset=utf-8"，无法上传文件，而上传文件需要通过"application/form-data; charset=utf-8"的方式进行

OkHttp还提供了一个MultipartBody类，同样继承自RequestBody，可以以"application/form-data; charset=utf-8"进行文件上传，同时"application/form-data"不仅可以上传文件，也可以用于普通数据的提交

普通参数提交

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OkHttpClient client = new OkHttpClient();
MultipartBody multipartBody = new MultipartBody.Builder()
    .setType(MultipartBody.FORM)
    .addFormDataPart("param1", "value1")
    .addFormDataPart("param2", "value2")
    .addFormDataPart("param3", "value3")
    .build();
Request request = new Request.Builder()
    .url(url)
    .post(multipartBody)
    .build();
Call call = client.newCall(request);
call.enqueue(new Callback() {
    @Override
    public void onFailure(Call call, IOException e) {
    }

    @Override
    public void onResponse(Call call, Response response) throws IOException {
        String result = response.body().string();
    }
}

MultipartBody在普通参数提交的时候，使用方式与FormBody基本一样，不过MultipartBody请求需要设置ContentType

文件上传

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OkHttpClient client = new OkHttpClient();
File file = new File("File path");
RequestBody requestBody = RequestBody.create(MediaType.parse("application/octet-stream"), file);
MultipartBody multipartBody = new MultipartBody.Builder()
    .setType(MultipartBody.FORM)
    .addFormDataPart("param1", "value1")
    .addFormDataPart("param2", "value2")
    .addFormDataPart("param3", "value3")
    .addFormDataPart("pic", "1.png", requestBody)
    .build();
Request request = new Request.Builder()
    .url(url)
    .post(multipartBody)
    .build();
Call call = client.newCall(request);
call.enqueue(new Callback() {
    @Override
    public void onFailure(Call call, IOException e) {
    }

    @Override
    public void onResponse(Call call, Response response) throws IOException {
        String result = response.body().string();
    }
}

文件依然是通过addFormDataPart进行添加，只不过多了一个RequestBody参数
将文件存放到RequestBody中，然后将该RequestBody添加到MultipartBody中，组成一个完整的RequestBody用于请求
“application/octet-stream”是以文件流方式传输，适合于所有文件，也可以使用指定的Content-Type进行传输，比如"application/x-png"

通过MultipartBody就可以轻松将文件上传至服务器，无需进行复杂的流操作，但是美中不足的是没有进度信息，如果文件较大的情况下，上传耗时比较久，只有文件完全上传后才有回调，十分不友好

文件上传-进度

OkHttp并没有提供进度的相关回调或者接口，但是POST都是通过RequestBody进行请求的，查看RequestBody类就可以发现RequestBody只有三个主要方法

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/** Returns the Content-Type header for this body. */
public abstract @Nullable MediaType contentType();

/**
* Returns the number of bytes that will be written to {@code sink} in a call to {@link #writeTo},
 * or -1 if that count is unknown.
 */
public long contentLength() throws IOException {
  return -1;
}

/** Writes the content of this request to {@code sink}. */
public abstract void writeTo(BufferedSink sink) throws IOException;

根据注释可以明确各个方法的作用

  1. contentType() 返回Content-Type
  2. contentLength() 返回已写入数据大小
  3. writeTo 将数据写入BufferedSink

RequestBody还提供了几个请求的实现，当上传文件的时候的实现方法：

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/** Returns a new request body that transmits the content of {@code file}. */
public static RequestBody create(final @Nullable MediaType contentType, final File file) {
  if (file == null) throw new NullPointerException("file == null");

  return new RequestBody() {
    @Override public @Nullable MediaType contentType() {
      return contentType;
    }

    @Override public long contentLength() {
      return file.length();
    }

    @Override public void writeTo(BufferedSink sink) throws IOException {
      Source source = null;
      try {
        source = Okio.source(file);
        sink.writeAll(source);
      } finally {
        Util.closeQuietly(source);
      }
    }
  };
}

因此只要获取BufferedSink的大小就可以获取文件传输的大小，但是OkHttp提供的方法中是将文件通过writeAll()进行写入的，无法确定每个时间段具体传输了多少，继续查看writeAll()

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@Override public long writeAll(Source source) throws IOException {
    if (source == null) throw new IllegalArgumentException("source == null");
    long totalBytesRead = 0;
    for (long readCount; (readCount = source.read(this, Segment.SIZE)) != -1; ) {
      totalBytesRead += readCount;
    }
    return totalBytesRead;
  }

到这就很明了了，writeAll每次写入的是Segment.SIZE(8192)字节，我们只要将writeAll提取出来就可以自己控制上传的进度了

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public class ProgressRequestBody extends RequestBody {
    private MediaType contentType;
    private File file;
    private ProgressCallback mCallback;

    public ProgressRequestBody(MediaType contentType, File file, ProgressCallback mCallback) {
        this.contentType = contentType;
        this.file = file;
        this.mCallback = mCallback;
    }
  @Override public @Nullable MediaType contentType() {
    return contentType;
  }

  @Override public long contentLength() {
    return file.length();
  }

  @Override public void writeTo(BufferedSink sink) throws IOException {
    Source source = null;
    try {
      source = Okio.source(file);
      long totalBytesRead = 0;
      for (long readCount; (readCount = source.read(this, Segment.SIZE)) != -1; ) {
        totalBytesRead += readCount;
        mCallback.uploadProgress(totalBytesRead);
      }
    } finally {
      Util.closeQuietly(source);
    }
  }
  
  public interface ProgressCallback{
      void uploadProgress(long totalBytesRead);
  }
}

调用的时候也只需要将

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RequestBody requestBody = RequestBody.create(MediaType.parse("application/octet-stream"), file);

替换成

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RequestBody requestBody = new ProgressRequestBody(MediaType.parse("application/octet-stream"), file);

就可以了

okhttp3