我的代码开始变得有点难以调试，这让我相信我的设计选择并不理想。我是一名 Android 编程新手，希望在简化设计以实现最佳操作方面得到一些帮助。
介绍
我正在编写一个使用 rfcomm 接口在客户端和服务器设备之间传输数据的应用程序。客户端需要使用特定的密钥向服务器请求某些东西，然后它需要等到服务器将结果发回。
当前设计
- 按下按钮会触发来自服务器的信息请求。
- 启动一个执行请求的新线程。
- 作为唯一整数的密钥被转换为字节数组并发送到服务器。
- 线程有一个 while 循环，它正在等待特定的布尔值从 false 翻转为 true，指示服务器返回的响应。
- 在服务器端接收信息。服务器使用密钥来确定下一步要做什么。
- 服务器启动一个线程来运行一些查询并得到一个 jsonString 作为结果。
- 服务器将转换为字节数组的 jsonstring 以相同的标识密钥发送回客户端。
- 客户端读取消息，并根据识别键将字节数组发送给处理方法。
- 处理方法将 jsonString 存储到类变量中，然后翻转布尔值以让其他线程知道它正在等待的值已被设置。
- Json 字符串在客户端转换为对象。对那个对象做了一些事情。
此代码当前正确地将信息发送到服务器，服务器正确搜索并获得有效的 json 字符串结果。但是，当服务器将其结果写入客户端时会出现此问题。我收到 20 条消息而不是 1 条消息，但没有一条与搜索键匹配...
我的问题
- 我是否以设计明智的有效方式做事？
- 我可以从使用
synchronized关键字 or 和 Atomic Boolean 使我的代码更线程安全中受益吗？我将如何实施它？ - 将字符串转换为字节数组是否有最大长度？也许代码试图为我中断发送，这就是为什么我得到 20 个不同的结果？
相关代码
public class ClientSpokesmanClass {
private final int searchKey = 2222222; //set the key to some int.
private boolean pendingSearchResults = false;
List<Place> places = new ArrayList<Place>();
private final Handler handler = new Handler(){
@Override
public void handleMessage(Message msg){
switch(msg.what) {
...
case MESSAGE_READ:
//Message received from server
readAndDistribute(msg.arg1, msg.obj);
break;
...
}
}
};
public List<Place> getPlacesFromServer(String query){
//ask server for search results
requestSearchFromServer(query);
//just wait for them...
while (pendingSearchResults){
//just waiting
}
return places;
}
private void requestSearchFromConnectedDevice(String query) {
if (mBluetoothState == STATE_CONNECTED){
byte[] bites = new byte[4];
bites = ByteBuffer.wrap(bites).putInt(searchKey).array();
byte[] stringBytes = null;
try {
stringBytes = query.getBytes("UTF-8");
} catch (UnsupportedEncodingException e) {
// TODO Auto-generated catch block
Log.e(TAG, "unsupported encoding", e);
}
int keyLength = bites.length;
int stringLength = stringBytes.length;
byte[] combined = new byte[keyLength+stringLength];
System.arraycopy(bites, 0, combined, 0, keyLength);
System.arraycopy(stringBytes, 0, combined, keyLength, stringLength);
mBluetoothService.write(combined);
}
pendingSearchResults = true;
}
private void receiveSearchResults(byte[] bites){
String jsonString = "";
PlacesJSONParser parser = new PlacesJSONParser();
try {
jsonString = new String(bites, "UTF-8");
} catch (UnsupportedEncodingException e) {
// TODO Auto-generated catch block
Log.e(TAG, "unsupported encoding", e);
}
if (D) Log.d(TAG, "Json string we got is "+jsonString);
try {
places = parser.parse(new JSONObject(jsonString));
} catch (JSONException e) {
// TODO Auto-generated catch block
Log.e(TAG, "JSON exception", e);
}
pendingSearchResults = false;
}
/**
* Reads come here first. Then, based on the key prepended to them,
* they then go to other methods for further work.
* @param bytes
* @param buffer
*/
private synchronized void readAndDistribute(int bytes, Object buffer){
byte[] buff = (byte[]) buffer;
int key = ByteBuffer.wrap(Arrays.copyOfRange(buff, 0, 4)).getInt();
if (key == searchKey){
receiveSearchResults(Arrays.copyOfRange(buff, 4, bytes));
}else{
//do something else
}
}
}
.
public class ClientUI extends Activity {
...
onQueryTextSubmit(String query){
final String queryFinal = query;
Thread thread = new Thread(){
public void run() {
places = ClientSpokesmanClass.getPlacesFromServer(query);
doSomethingWithPlaces();
}
};
thread.start();
}
}
.
public class ServerReceive {
private searchKey = 2222222;
...
//code that handles messages, reads key, and then runs doSearchAndWriteResults()
...
private synchronized void doSearchAndWriteResults(byte[] bites){
if (D) Log.d(TAG, "+++writeSearchResults");
//Initialize query and placesString
String query = null;
String placesString;
//Convert byte array to the query string
try {
query = new String(bites, "UTF-8");
} catch (UnsupportedEncodingException e) {
// TODO Auto-generated catch block
Log.e(TAG, "unsupported encoding",e);
}
//if the string was converted successfully...
if (query != null){
//Run the places query and set the json string to placesString
if (D) Log.d(TAG, "query is "+query);
PlacesProvider placeProvider = new PlacesProvider();
placesString = placeProvider.getPlacesString(query);
}
//initialize a bite array
byte[] stringBytes = null;
try {
//convert jsonString to byte array
stringBytes = placesString.getBytes("UTF-8");
} catch (UnsupportedEncodingException e) {
// TODO Auto-generated catch block
Log.e(TAG, "unsupported encoding",e);
}
//Put the search key to a byte array. I am using this key on the client side
//to confirm that we are reading searchResults and not some other type of write.
byte[] bite = new byte[4];
bite = ByteBuffer.wrap(bite).putInt(searchKey).array();
//Get the lengths of the two byte arrays
int keyLength = bite.length;
int stringLength = stringBytes.length;
//combine the byte arrays for sending
byte[] combined = new byte[keyLength+stringLength];
System.arraycopy(bite, 0, combined, 0, keyLength);
System.arraycopy(stringBytes, 0, combined, keyLength, stringLength);
if (D) Log.d(TAG, "Actually writing things here...");
//send the byte arrrays over rfcomm
mBluetoothService.write(combined);
}
}