我想通过使用ParcelFileDescriptor.createPipe()
、流到流复制线程和ParcelFileDescriptor将InputStream从一个Android服务"发送"到另一个在不同进程中运行的服务,ParcelFile描述符表示管道的读取端,通过Binder IPC将其提供给另一个服务。
发送代码(进程A)
我想将给定的InputStream发送到接收服务:
public sendInputStream() {
InputStream is = ...; // that's the stream for process/service B
ParcelFileDescriptor pdf = ParcelFileDescriptorUtil.pipeFrom(is);
inputStreamService.inputStream(pdf);
}
ParcelFileDescriptorUtil是一个助手类,具有经典的java.io.
流到流复制Thread:
public class ParcelFileDescriptorUtil {
public static ParcelFileDescriptor pipeFrom(InputStream inputStream) throws IOException {
ParcelFileDescriptor[] pipe = ParcelFileDescriptor.createPipe();
ParcelFileDescriptor readSide = pipe[0];
ParcelFileDescriptor writeSide = pipe[1];
// start the transfer thread
new TransferThread(inputStream, new ParcelFileDescriptor.AutoCloseOutputStream(writeSide)).start();
return readSide;
}
static class TransferThread extends Thread {
final InputStream mIn;
final OutputStream mOut;
TransferThread(InputStream in, OutputStream out) {
super("ParcelFileDescriptor Transfer Thread");
mIn = in;
mOut = out;
setDaemon(true);
}
@Override
public void run() {
byte[] buf = new byte[1024];
int len;
try {
while ((len = mIn.read(buf)) > 0) {
mOut.write(buf, 0, len);
}
mOut.flush(); // just to be safe
} catch (IOException e) {
LOG.e("TransferThread", e);
}
finally {
try {
mIn.close();
} catch (IOException e) {
}
try {
mOut.close();
} catch (IOException e) {
}
}
}
}
}
接收服务代码(流程B)
接收服务的.aidl
:
package org.exmaple;
interface IInputStreamService {
void inputStream(in ParcelFileDescriptor pfd);
}
接收服务,由进程A调用:
public class InputStreamService extends Service {
@Override
public IBinder onBind(Intent intent) {
return mBinder;
}
private final IInputStreamService.Stub mBinder = new IInputStreamService.Stub() {
@Override
public void inputStream(ParcelFileDescriptor pfd) throws RemoteException {
InputStream is = new ParcelFileDescriptor.AutoCloseInputStream(pfd);
OutputStream os = ...;
int len;
byte[] buf = new byte[1024];
try {
while ((len = is.read(buf)) > 0) {
os.write(buf, 0, len);
}
} catch (IOException e) {
// this catches the exception shown below
}
}
};
但inputStream()
中的in.read()
总是抛出一个IOException
java.io.IOException: read failed: EBADF (Bad file number)
at libcore.io.IoBridge.read(IoBridge.java:442)
at java.io.FileInputStream.read(FileInputStream.java:179)
at java.io.InputStream.read(InputStream.java:163)
当文件描述符关闭时,EBADF errno似乎是由read()
设置的。但我不知道是什么原因造成的,也不知道如何修复
是的,我知道ConentProvider也有可能。但它不应该也适用于我的方法吗?有没有其他方法可以将InputStream流交给Android中的不同服务?
附带说明:CommonsWare使用ContentProvider创建了一个类似的项目(相关SO问题1、2)。这是我从
原因似乎是ParcelFileDescriptor
是服务方法的参数。如果服务确实返回ParcelFileDescriptor
,它将按预期工作。
发送服务(进程A)
public void sendInputStream() {
InputStream is = ...; // that's the stream for process/service B
ParcelFileDescriptor pfd = inputStreamService.inputStream();
OutputStream os = new ParcelFileDescriptor.AutoCloseOutputStream(pfd);
int len;
byte[] buf = new byte[1024];
try {
while ((len = is.read(buf)) > 0) {
os.write(buf, 0, len);
}
} catch (IOException e) {
} finally {
try { is.close(); } catch (IOException e1) {}
try { os.close(); } catch (IOException e1) {}
}
}
接收服务代码(流程B)
接收服务的.aidl
:
package org.exmaple;
interface IInputStreamService {
ParcelFileDescriptor inputStream();
}
接收服务,由进程A调用:
public class InputStreamService extends Service {
@Override
public IBinder onBind(Intent intent) {
return mBinder;
}
private final IInputStreamService.Stub mBinder = new IInputStreamService.Stub() {
@Override
public void ParcelFileDescriptor inputStream() throws RemoteException {
// one can read the contents of the Processes A's InputStream
// from the following OutputStream
OutputStream os = ...;
ParcelFileDescriptor pfd = ParcelFileDescriptorUtil.pipeTo(os);
return pfd;
}
};
ParcelFileDescriptorUtil是一个助手类,具有经典的java.io.
流到流复制线程现在我们必须使用pipeTo()
方法。
public class ParcelFileDescriptorUtil {
public static ParcelFileDescriptor pipeTo(OutputStream outputStream) throws IOException {
ParcelFileDescriptor[] pipe = ParcelFileDescriptor.createPipe();
ParcelFileDescriptor readSide = pipe[0];
ParcelFileDescriptor writeSide = pipe[1];
// start the transfer thread
new TransferThread(new ParcelFileDescriptor.AutoCloseInputStream(readSide), outputStream).start();
return writeSide;
}
static class TransferThread extends Thread {
final InputStream mIn;
final OutputStream mOut;
TransferThread(InputStream in, OutputStream out) {
super("ParcelFileDescriptor Transfer Thread");
mIn = in;
mOut = out;
setDaemon(true);
}
@Override
public void run() {
byte[] buf = new byte[1024];
int len;
try {
while ((len = mIn.read(buf)) > 0) {
mOut.write(buf, 0, len);
}
mOut.flush(); // just to be safe
} catch (IOException e) {
LOG.e("TransferThread", e);
}
finally {
try {
mIn.close();
} catch (IOException e) {
}
try {
mOut.close();
} catch (IOException e) {
}
}
}
}
}
这允许您跨进程边界传输InputStreams,一个缺点是流到流拷贝中涉及一些CPU时间。