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Android跨进程传递大数据 Android跨进程传递大数据的方法实现

R7_Perfect 人气:0
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最近要从Service端给Client端传递图片数据,之前的数据都是通过aidl传递:

创建 Parcelable文件

ImageData.java

public class ImageData implements Parcelable {
  private byte[] data;
  public byte[] getData() {
    return data;
  }

  public ImageData(byte[] dataIn) {
    this.data = dataIn;
  }

  public ImageData(Parcel in) {
    int arrayLength = in.readInt();
    if (arrayLength > 0) {
      data = new byte[arrayLength];
      in.readByteArray(data);
    }
  }

  @Override
  public void writeToParcel(Parcel dest, int flags) {
    if (data != null && data.length > 0) {
      dest.writeInt(data.length);
      dest.writeByteArray(data);
    } else {
      dest.writeInt(0);
    }
  }
  ...
}

test.aidl
interface test {
  void sendMessage(ImageData data);
}

运行报错:

    android.os.DeadObjectException: Transaction failed on small parcel; remote process probably died
        at android.os.BinderProxy.transactNative(Native Method)
        at android.os.BinderProxy.transact(BinderProxy.java:514)
        ...

原因

这里导致DeadObjectException的原因主要是binder创建的buffer被占满了:

kernel/msm-4.4/drivers/android/binder_alloc.c
 315     if (best_fit == NULL) {
...
341         pr_err("%d: binder_alloc_buf size %zd failed, no address space\n",
342                   alloc->pid, size);
343         pr_err("allocated: %zd (num: %zd largest: %zd), free: %zd (num: %zd largest: %zd)\n",
344                       total_alloc_size, allocated_buffers, largest_alloc_size,
345                  total_free_size, free_buffers, largest_free_size);
346            eret = ERR_PTR(-ENOSPC);
347              goto error_unlock;
348    }

传输中如果数据大于free_buffers,则会抛出DeadObjectException

解决

1.socket
socke传输不受大小限制,但实现比较复杂

2.文件
通过文件传输比较简单,但效率差,而且高版本会受到Android系统权限限制

3.数据切割
将较大数据切割成较小的数据传输,此方法是兼顾效率,复杂度较好的方案

定义数据体:

public class SliceData implements Parcelable {
  private byte[] data;
  private int length;
  ...
}

切割数据方法:

  public static byte[][] divideArray(byte[] source, int chunkSize) {
    int totalLength = source.length;
    int arraySize = (int) Math.ceil(totalLength / (double) chunkSize);
    byte[][] ret = new byte[arraySize][chunkSize];
    int start = 0;
    int parts = 0;
    for (int i = 0; i < arraySize; i++) {
      if (start + chunkSize > totalLength) {
        System.arraycopy(source, start, ret[i], 0, source.length - start);
      } else {
        System.arraycopy(source, start, ret[i], 0, chunkSize);
      }
      start += chunkSize;
      parts++;
    }
    return ret;
  }

将SliceData按顺序构建发送:

byte[][] divideData = divideArray(testBytes, 64 * 1024);//64k
for (byte[] item : divideData) {
  mEmitter.onNext(new SliceData(length, item));
}

client接收:

int chunkSize = bytes.length;
if(buffer == null) {
  buffer = new byte[length];
  index = 0;
}
if (index + chunkSize > bodyLength) {//最后一个数据块
  System.arraycopy(bytes, 0, buffer, index, bodyLength - index);
  visualResultData.bitmap = BitmapFactory.decodeByteArray(buffer, 0, buffer.length);
  buffer = null;
  index = 0;
} else {
  System.arraycopy(bytes, 0, buffer, index, chunkSize);
  index += chunkSize;
}

4.第三方
binder本身也是利用mmap,可以利用实现mmap的框架,比如 MMKV

5.Bitmap
如果传输的数据是Bitmap,还可以用Bundle的putBinder方案
定义binder:

class ImageBinder extends IRemoteGetBitmap.Stub {
  @Override
  public Bitmap getBitMap() throws RemoteException {
    return mBitmap;
  }
}

发送

Bundle bundle = new Bundle();
bundle.putBinder("bitmap", new ImageBinder());
intent.putExtras(bundle);

接收:

ImageBinder imageBinder = (ImageBinder) bundle.getBinder("bitmap");
Bitmap bitmap = imageBinder.getBitmap();

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