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有关Android NIO的相关内容，本次整理并归类如下，为了让大家感觉NIO和Android平台联系的紧密，这里我们结合ADT插件的重要开发工具DDMS中的源码进行分析。在android git中的sdk.git文件中，可以找到ddmlib这个文件夹。有关PC和手机的互通内核在这里使用了java来完全实现。这里一起帮助大家了解下PC同步软件的开发原理同时学习下Java中的New I/O技术。 比较重要的代码段我们贴出，逐一分析，其他的网友可以直接预读源码:
AdbHelper.java文件中 public static SocketChannel open(InetSocketAddress adbSockAddr,
Device device, int devicePort) //这是一个重载版本，主要是关联Device实例。
throws IOException, TimeoutException, AdbCommandRejectedException {
SocketChannel adbChan = SocketChannel.open(adbSockAddr); //构造SocketChannel对象，使用常规的open方法创建
try {
adbChan.socket().setTcpNoDelay(true); //设置TCP非延迟
adbChan.configureBlocking(false); //非阻塞
setDevice(adbChan, device); //本句和NIO没有多大关系，这句是指定具体的设备，比如模拟器，或Android手机的厂家代号，比如宏达电的以HTXXXXX这样的方式
byte[] req = createAdbForwardRequest(null, devicePort); //设置端口转发，这句很关键，否则PC和手机通过USB是无法互通的。
write(adbChan, req); //发送数据
AdbResponse resp = readAdbResponse(adbChan, false); //读取收到的内容
if (resp.okay == false) {
throw new AdbCommandRejectedException(resp.message);
}
adbChan.configureBlocking(true);
} catch (TimeoutException e) { //一般要处理超时异常
adbChan.close(); //释放channel句柄
throw e;
} catch (IOException e) { //处理常规的IO异常
adbChan.close();
throw e;
}
return adbChan;
}
复制代码有关读取ADB返回的报文方法 static AdbResponse readAdbResponse(SocketChannel chan, boolean readDiagString)
throws TimeoutException, IOException {
AdbResponse resp = new AdbResponse();
byte[] reply = new byte[4]; //创建4字节数组，主要检测成功与否，adb的协议是成功返回 okay，失败fail，等等。
read(chan, reply); //读取具体的返回
if (isOkay(reply)) { //判断是否成功
resp.okay = true;
} else {
readDiagString = true; // look for a reason after the FAIL
resp.okay = false;
}
// not a loop -- use "while" so we can use "break"
try {
while (readDiagString) {
// length string is in next 4 bytes
byte[] lenBuf = new byte[4];
read(chan, lenBuf); //读取一个字节数组，最终为了转为一个整形
String lenStr = replyToString(lenBuf); //字节数组转为String
int len;
try {
len = Integer.parseInt(lenStr, 16); //String转为整形，这里提示，这种写法可能比较愚蠢，但是下面为Log输出提供了一点点的便利。
} catch (NumberFormatException nfe) {
Log.w("ddms", "Expected digits, got '" + lenStr + "': "
+ lenBuf[0] + " " + lenBuf[1] + " " + lenBuf[2] + " "
+ lenBuf[3]);
Log.w("ddms", "reply was " + replyToString(reply));
break;
}
byte[] msg = new byte[len];
read(chan, msg);
resp.message = replyToString(msg);
Log.v("ddms", "Got reply '" + replyToString(reply) + "', diag='"
+ resp.message + "'");
break;
}
} catch (Exception e) {
// ignore those, since it's just reading the diagnose string, the response will
// contain okay==false anyway.
}
return resp;
}
有关PC上对Android手机屏幕截图的方法之一:
static RawImage getFrameBuffer(InetSocketAddress adbSockAddr, Device device)
throws TimeoutException, AdbCommandRejectedException, IOException {
RawImage imageParams = new RawImage();
byte[] request = formAdbRequest("framebuffer:"); // 读取手机端adbd服务器的framebuffer调用返回的数组
byte[] nudge = {
0
};
byte[] reply;
SocketChannel adbChan = null;
try {
adbChan = SocketChannel.open(adbSockAddr);
adbChan.configureBlocking(false); //非阻塞
setDevice(adbChan, device); //设置我们关系的设备
write(adbChan, request); //发送framebuffer这个请求了
AdbResponse resp = readAdbResponse(adbChan, false /* readDiagString */);
if (resp.okay == false) { //判断返回是否ok。
throw new AdbCommandRejectedException(resp.message);
}
reply = new byte[4];
read(adbChan, reply); //首先返回的是一个协议，目前分为两个版本，主要是兼容模式和标准的模式，兼容模式比较少见，在2.0以后几乎看不到了。部分早期的1.6或更老的T-Mobile G1会使用兼容模式，模式不同，输出的截图中的颜色编码方式略有不同。
ByteBuffer buf = ByteBuffer.wrap(reply);
buf.order(ByteOrder.LITTLE_ENDIAN); //小头字节顺序
int version = buf.getInt(); //ByteBuffer直接转int的方法，比较方便不用自己从字节数组中构造，按位计算
int headerSize = RawImage.getHeaderSize(version); //根据返回的adb截图协议版本判断将收到的字节大小
reply = new byte[headerSize * 4]; //分配空间，具体大小需要看协议版本
read(adbChan, reply);
buf = ByteBuffer.wrap(reply); //从reply数组实例化ByteBuffer
buf.order(ByteOrder.LITTLE_ENDIAN); //注意字节序列，毕竟远端的adbd是工作在linux系统的手机上。
if (imageParams.readHeader(version, buf) == false) { //判断是否有效，兼容这种截图协议。
Log.e("Screenshot", "Unsupported protocol: " + version);
return null;
}
Log.d("ddms", "image params: bpp=" + imageParams.bpp + ", size="
+ imageParams.size + ", width=" + imageParams.width
+ ", height=" + imageParams.height); //打印下截图的基本信息，比如bpp代表色深，size是需要分配dib图像的字节数组。比较原始，
write(adbChan, nudge); //发送一个字节，代表准备接收字节数组了
reply = new byte[imageParams.size]; //分配和图像大小一样的字节数组
read(adbChan, reply); //接收图像字节数组，这里Android开发网提示大家对于Android 1.x可能为RGB565，分配大小为 wxhx2xsize ，而2.x以后基本上为32位的RGB8888，分配大小为wxhx4xsize
imageParams.data = reply;
} finally {
if (adbChan != null) {
adbChan.close();
}
}
return imageParams;
}
复制代码继续就Android DDMS源码一起分析NIO非阻塞通讯方式，给大家分享下手机和PC互通中的一些技术。在NIO中有关SocketChannel和ByteBuffer的使用细节，可以在今天文章中 static void read(SocketChannel chan, byte[] data, int length, int timeout)
throws TimeoutException, IOException {
ByteBuffer buf = ByteBuffer.wrap(data, 0, length != -1 ? length : data.length); //从字节数组中实例化ByteBuffer
int numWaits = 0;
while (buf.position() != buf.limit()) { //循环接收数据
int count;
count = chan.read(buf);
if (count < 0) {
throw new IOException("EOF"); //读到末尾
} else if (count == 0) {
if (timeout != 0 && numWaits * WAIT_TIME > timeout) {
throw new TimeoutException();
}
try {
Thread.sleep(WAIT_TIME);
} catch (InterruptedException ie) {
}
numWaits++;
} else {
numWaits = 0;
}
}
}
复制代码有关SocketChannel的写操作，就是发送数据代码如下: static void write(SocketChannel chan, byte[] data, int length, int timeout)
throws TimeoutException, IOException {
ByteBuffer buf = ByteBuffer.wrap(data, 0, length != -1 ? length : data.length);
int numWaits = 0;
while (buf.position() != buf.limit()) {
int count;
count = chan.write(buf); //发送数据从ByteBuffer中
if (count < 0) {
throw new IOException("channel EOF");
} else if (count == 0) {
if (timeout != 0 && numWaits * WAIT_TIME > timeout) {
throw new TimeoutException();
}
try {
Thread.sleep(WAIT_TIME);
} catch (InterruptedException ie) {
}
numWaits++;
} else {
numWaits = 0;
}
}
}
复制代码有关ADB如何选择一个具体的设备，可以使用 setDevice 方法，这样当电脑中有模拟器或链接了多个手机，可以通过设备序列号，选择需要通讯的设备。 static void setDevice(SocketChannel adbChan, IDevice device)
throws TimeoutException, AdbCommandRejectedException, IOException {
// if the device is not -1, then we first tell adb we're looking to talk
// to a specific device
if (device != null) {
String msg = "host:transport:" + device.getSerialNumber(); // 最后的获取序列号，提示大家在adb命令中是adb get-serialno
byte[] device_query = formAdbRequest(msg);
write(adbChan, device_query);
AdbResponse resp = readAdbResponse(adbChan, false /* readDiagString */);
if (resp.okay == false) {
throw new AdbCommandRejectedException(resp.message,
true/*errorDuringDeviceSelection*/);
}
}
}
通过PC控制手机重启的代码，当然这里需要Root权限才能执行
public static void reboot(String into, InetSocketAddress adbSockAddr,
Device device) throws TimeoutException, AdbCommandRejectedException, IOException {
byte[] request;
if (into == null) {
request = formAdbRequest("reboot:"); //$NON-NLS-1$
} else {
request = formAdbRequest("reboot:" + into); //$NON-NLS-1$
}
SocketChannel adbChan = null;
try {
adbChan = SocketChannel.open(adbSockAddr);
adbChan.configureBlocking(false);
// if the device is not -1, then we first tell adb we're looking to talk
// to a specific device
setDevice(adbChan, device);
write(adbChan, request);
} finally {
if (adbChan != null) {
adbChan.close();
}
}
}
复制代码
Android开发进阶之NIO非阻塞包（一）Android开发进阶之NIO非阻塞包(二)
Android开发进阶之NIO非阻塞包（四） |
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发表于 2011-10-24 10:50:41