Android跨进程传递大数据的方法实现
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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