I am using JNA to access User32 functions (I dont think it has got to do with Java here, more of concept problem). In my application, I have a Java process which communicates with the Canon SDK. To dispatch any messages I am using the below function:
private void peekMessage(WinUser.MSG msg) throws InterruptedException {
int hasMessage = lib.GetMessage(msg, null, 0, 0);
if (hasMessage != 0) {
lib.TranslateMessage(msg);
lib.DispatchMessage(msg);
}
Thread.sleep(1);
}
peekMessage is called in a loop and it all works well. Whenever an Image is taken from camera, I get the event and do the rest.
But I have observed, say after about 15 seconds (sometimes never or sometimes just at start) of no activity with camera, taking picture does not give me any download event. Later the whole application becomes unusable as it doesn't get any events from camera.
What can be the reason for this? Please let me know of any other info needed, I can paste the respective code along.
Edit:
Initialization:
Map<String, Integer> options = new HashMap<String, Integer>();
lib = User32.INSTANCE;
hMod = Kernel32.INSTANCE.GetModuleHandle("");
options.put(Library.OPTION_CALLING_CONVENTION, StdCallLibrary.STDCALL_CONVENTION);
this.EDSDK = (EdSdkLibrary) Native.loadLibrary("EDSDK/dll/EDSDK.dll", EdSdkLibrary.class, options);
private void runNow() throws InterruptedException {
while (!Thread.currentThread().isInterrupted()) {
Task task = queue.poll();
if (task != null) {
int taskResult = task.call();
switch (taskResult) {
case (Task.INITIALIZE_STATE):
break;
case (Task.PROCESS_STATE):
break;
case (Task.TERMINATE_STATE): {
//queue.add(new InitializeTask());
Thread.currentThread().interrupt();
break;
}
default:
;
}
}
getOSEvents();
}
}
WinUser.MSG msg = new WinUser.MSG();
private void getOSEvents() throws InterruptedException {
if (isMac) {
receiveEvents();
} else {
peekMessage(msg);
}
}
Above, whenever I get my camera event, it add's it to the queue and in each loop I check the queue to process any Task. One more important information: This is a process running on cmd and has no window. I just need the events from my camera and nothing else.
The code where I register callback functions:
/**
* Adds handlers.
*/
private void addHandlers() {
EdSdkLibrary.EdsVoid context = new EdSdkLibrary.EdsVoid(new Pointer(0));
int result = EDSDK.EdsSetObjectEventHandler(edsCamera, new NativeLong(EdSdkLibrary.kEdsObjectEvent_All), new ObjectEventHandler(), context).intValue();
//above ObjectEventHandler contains a function "apply" which is set as callback function
context = new EdSdkLibrary.EdsVoid(new Pointer(0));
result = EDSDK.EdsSetCameraStateEventHandler(edsCamera, new NativeLong(EdSdkLibrary.kEdsStateEvent_All), new StateEventHandler(), context).intValue();
//above StateEventHandler contains a function "apply" which is set as callback function
context = new EdSdkLibrary.EdsVoid(new Pointer(0));
result = EDSDK.EdsSetPropertyEventHandler(edsCamera, new NativeLong(EdSdkLibrary.kEdsStateEvent_All), new PropertyEventHandler(), context).intValue();
//above PropertyEventHandler contains a function "apply" which is set as callback function
}
You are getting ALL messages from ALL windows that belong to this thread, that includes all mouse moves, paints etc. if you aren't rapidly calling this function your message queue will overflow and cause the behavior you describe.
The sleep you definitely don't want as GetMessage yields if no message is waiting.
So if there exists a normal message pump(s) (i.e GetMessage/DispatchMessage) loop somewhere else for this threads window(s) then you should let that pump do most of the work, perhaps use wMsgFilterMin, wMsgFilterMax to just get the event message you require; or even better in this case use peekmessage with PM_NOREMOVE (then you will need your sleep
call as peekmessage returns immediately).
Alternatively provide the hWnd of the window that generates the event to reduce the workload.
Use spy++ to look into which windows this thread owns and what messages are being produced.
To take this answer further please provide answers to: what else is this thread doing and what windows does it own; also is this message pump the only one or do you call into the SDK API where it may be pumping messages too?
There is an OpenSource project wrapping EDSDK with JNA and it has a version of your code that is probably working better:
https://github.com/kritzikratzi/edsdk4j/blob/master/src/edsdk/api/CanonCamera.java#L436
Unfortunately this is not platform independent and specifically the way things work on windows. I am currently in the process of trying to get a MacOS version of things working at:
https://github.com/WolfgangFahl/edsdk4j
Related
This question is about running a non-blocking, high-performance activity in nativescript that is needed for the simple task of reading and saving raw audio from the microphone by directly accessing the hardware through the native Android API. I believe I have brought the nativescript framework to the edge of its capabilities, and I need experts' help.
I'm building a WAV audio recorder in Nativescript Android. Native implementation is described here (relevant code below).
In short, this can be done by reading audio steam from an android.media.AudioRecord buffer, and then writing the buffer to a file in a separate thread, as described:
Native Android implementation
startRecording() is triggered by a button press, and starts a new Thread that runs writeAudioDataToFile():
private void startRecording() {
// ... init Recorder
recorder.startRecording();
isRecording = true;
recordingThread = new Thread(new Runnable() {
#Override
public void run() {
writeAudioDataToFile();
}
}, "AudioRecorder Thread");
recordingThread.start();
}
Recording is stopped by setting isRecording to false (stopRecording() is triggered by a button press):
private void stopRecording() {
isRecording = false;
recorder.stop();
recorder.release();
recordingThread = null;
}
Reading and saving buffer is stopped if isRecording = false:
private void writeAudioDataToFile() {
// ... init file and buffer
ByteArrayOutputStream recData = new ByteArrayOutputStream();
DataOutputStream dos = new DataOutputStream(recData);
int read = 0;
while(isRecording) {
read = recorder.read(data, 0, bufferSize);
for(int i = 0; i < bufferReadResult; i++) {
dos.writeShort(buffer[i]);
}
}
}
My Nativescript javascript implementation:
I wrote a nativescript typescript code that does the same as the native Android code above. The problem #1 I faced was that I can't run while(isRecording) because the javascript thread would be busy running inside the while loop, and would never be able to catch button clicks to run stopRecording().
I tried to solve problem #1 by using setInterval for asynchronous execution, like this:
startRecording() is triggered by a button press, and sets a time interval of 10ms that executes writeAudioDataToFile():
startRecording() {
this.audioRecord.startRecording();
this.audioBufferSavingTimer = setInterval(() => this.writeAudioDataToFile(), 10);
}
writeAudioDataToFile() callbacks are queued up every 10ms:
writeAudioDataToFile() {
let bufferReadResult = this.audioRecord.read(
this.buffer,
0,
this.minBufferSize / 4
);
for (let i = 0; i < bufferReadResult; i++) {
dos.writeShort(buffer[i]);
}
}
Recording is stopped by clearing the time interval (stopRecording() is triggered by button press):
stopRecording() {
clearInterval(this.audioBufferSavingTimer);
this.audioRecord.stop();
this.audioRecord.release();
}
Problem #2: While this works well, in many cases it makes the UI freeze for 1-10 seconds (for example after clicking a button to stop recording).
I tried to change the time interval that executes writeAudioDataToFile() from 10ms to 0ms and up to 1000ms (while having a very big buffer), but then the UI freezes were longer and, and I experienced loss in the saved data (buffered data that was not saved to the file).
I tried to offload this operation to a separate Thread by using a nativescript worker thread as described here, where startRecording() and stopRecording() are called by messages sent to the thread like this:
global.onmessage = function(msg) {
if (msg.data === 'startRecording') {
startRecording();
} else if (msg.data === 'stopRecording') {
stopRecording();
}
}
This solved the UI problem, but created problem #3: The recorder stop was not executed on time (i.e. recording stops 10 to 50 seconds after the 'stopRecording' msg.data is received by the worker thread). I tried to use different time intervals in the setInterval inside the worker thread (0ms to 1000ms) but that didn't solve the problem and even made stopRecording() be executed with greater delays.
Does anyone have an idea of how to perform such a non-blocking high-performance recording activity in nativescript/javascript?
Is there a better approach to solve problem #1 (javascript asynchronous execution) that I described above?
Thanks
I would keep the complete Java implementation in actual Java, you can do this by creating a java file in your plugin folder:
platforms/android/java, so maybe something like:
platforms/android/java/org/nativescript/AudioRecord.java
In there you can do everything threaded, so you won't be troubled by the UI being blocked. You can call the Java methods directly from NativeScript for starting and stopping the recording. When you build your project, the Java file will automatically be compiled and included.
You can generate typings from your Java class by grabbing classes.jar from the generated .aar file of your plugin ({plugin_name}.aar) and generate type declarations for it: https://docs.nativescript.org/core-concepts/android-runtime/metadata/generating-typescript-declarations
This way you have all the method/class/type information available in your editor.
I am trying to get my console application to simulate dragging and dropping a file, so far I have had no luck.
The system throws a win32 exception stating it cannot find the file, since I know that is not really the problem I was hoping someone could shed some light on what might be causing this behavior.
I suspect it might be DEP. I can drag and drop the file and the process runs as expected, but I need to automate this.
I have created a filewatcher and am right now trying to figure out how to get the code to work, prior to making it a windows service.
But right now I am really stuck on this win32 error.
public class Watcher
{
public static void Main(string[] args)
{
Run();
}
[PermissionSet(SecurityAction.Demand, Name = "FullTrust")]
public static void Run()
{
string[] args = System.Environment.GetCommandLineArgs();
// If a directory is not specified, exit program.
if (args.Length != 2)
{
// Display the proper way to call the program.
Console.WriteLine("Usage: Watcher.exe (directory)");
return;
}
// Create a new FileSystemWatcher and set its properties.
FileSystemWatcher watcher = new FileSystemWatcher();
watcher.Path = args[1];
/* Watch for changes in LastAccess and LastWrite times, and
the renaming of files or directories. */
watcher.NotifyFilter = NotifyFilters.LastAccess | NotifyFilters.LastWrite
| NotifyFilters.FileName | NotifyFilters.DirectoryName;
// Only watch jpg files.
watcher.Filter = "*.jpg";
// Add event handlers.
watcher.Changed += new FileSystemEventHandler(OnChanged);
watcher.Created += new FileSystemEventHandler(OnChanged);
watcher.Deleted += new FileSystemEventHandler(OnChanged);
watcher.Renamed += new RenamedEventHandler(OnRenamed);
// Begin watching.
watcher.EnableRaisingEvents = true;
// Wait for the user to quit the program.
Console.WriteLine("Press \'q\' to quit the sample.");
while (Console.Read() != 'q') ;
}
// Define the event handlers.
private static void OnChanged(object source, FileSystemEventArgs e)
{
// Specify what is done when a file is changed, created, or deleted.
Console.WriteLine("File: " + e.FullPath + " " + e.ChangeType);
Process.Start(e.FullPath + "c:\\demo\\kr-pano\\mpr.bat");
}
Visit the link to see the full win32 exception details.
Win32Exception
Apparently the issue is being caused because the filesystemwatcher is single threaded, and when I try to launch my new process it stops the old one from running. All I needed to do was stub out a new runpano function and call it from my code, its working now.
I am trying to fetch Customer data to parse them into customer object to display on TableView. The following code sometimes works, sometimes not. Whenever it does crash, it shows Customer data is empty in the foreach loop even though I run the same code every time. I do not have clue what could be wrong in this circumstances. I am quite new on this platform. If I am missing anything/ extra information, please let me know.
namespace TableViewExample
{
public partial class MyDataServices : ContentPage
{
private ODataClient mODataClient;
private IEnumerable <IDictionary<string,object>> Customers;
public MyDataServices ()
{
InitializeComponent ();
InitializeDataService ();
GetDataFromOdataService ();
TableView tableView = new TableView{ };
var section = new TableSection ("Customer");
foreach (var customers in Customers) {
//System.Diagnostics.Debug.WriteLine ((string)customers ["ContactName"]);
var name = (string)customers ["ContactName"];
var cell = new TextCell{ Text = name };
section.Add (cell);
}
tableView.Root.Add (section);
Padding = new Thickness (10, 20, 10, 10);
Content = new StackLayout () {
Children = { tableView }
};
}
private void InitializeDataService(){
try {
mODataClient = new ODataClient ("myURL is here");
}
catch {
System.Diagnostics.Debug.WriteLine("ERROR!");
}
}
private void GetDataFromOdataService (){
try {
Customers = mODataClient.For ("Customers").FindEntries ();
}
catch {
System.Diagnostics.Debug.WriteLine("ERROR!");
}
}
}
}
Its hard helping out here, however here are some things to consider:-
It sounds like the dataservice could either be not contactable / offline; too busy or it could even be throwing an exception itself and returning a data response that you are not expecting to receive, that then triggers an exception and crash in your application as your always expecting an exact response without catering for any abnormal responses / events.
If you are contacting an external service over the internet it may just be your internet connection is slow / faulty and not returning the information fast enough as other possibilities.
In your code you are assuming that you always get a response from the server - and that this response will always be of an anticipated structure that your expecting to decode - without factoring in any possibility of abnormal responses returned by the dataservice. I have not used ODataClient personally, so not sure how it behaves in the event of maybe no data received / timeout or in your case the dataservice and how it behaves internally in the response to a bad-request etc.
I am assuming an exception would get thrown, and you do get your debug line executed indicating a failure.
You may want to also adjust this statement so that you write out the exception as well, i.e.:-
private void GetDataFromOdataService ()
{
try
{
Customers = mODataClient.For ("Customers").FindEntries ();
}
catch (Exception ex)
{
System.Diagnostics.Debug.WriteLine("ERROR!" + ex.ToString());
}
}
If there was a bad response, then the line at Customers = ..... would throw the exception as there may be no Customers returned or some other information packaged in the response from the dataservice.
The Customers variable would also be null at this point I am assuming due to this failing.
So when you get back to your code at foreach (var customers in Customers) { it will then throw a null reference exception as Customers is infact null.
As all your current code executes in the constructor without any try and catch block around this, it will also crash your application at this point as well.
Also you are doing all of this work in the constructor. Try seperating this out. I haven't investigated exactly where the constructor gets called in an iOS page life-cycle, however, if it is in the viewDidLoad, then you have something like 10 seconds for everything to complete, otherwise it will exit automatically. I imagine in your case, this isn't applicable however.
Going forward also try putting your layout controls in the constructor, and move your data task to maybe the OnAppearing override instead.
Using async would definitely be advisable as well, but remember you need to inspect the response from your dataservice, as the error could be embedded within the response also and you will need to detect when it is OK to process the data.
I have written this code in c# application for tracking messages ...
protected override void WndProc(ref Message m)
{
// Listen for operating system messages.
switch (m.Msg)
{
case WM_CHAR:
FileStream fs = new FileStream("d:/Type.txt",FileMode.Append,FileAccess.Write);
//set up a streamwriter for adding text
StreamWriter sw = new StreamWriter(fs);
sw.BaseStream.Seek(0, SeekOrigin.End);
int no=(int)m.WParam;
sw.Write(Convert.ToChar(no));
sw.Flush();
sw.Close();
break;
}
base.WndProc(ref m);
}
I want to track messages for different window so how can I pass different window handle to wndproc ? please help me...
You'd have to register global keyboard hook instead of passing different handle. This article shows how to do that. Basic idea behind that is that you register your function for polling all keyboard-related system events (for every message) and filter out only those you need.
The functionality is achieved with SetWindowsHookEx winapi function.
You can filter all the messages in the application by calling Application.AddMessageFilter(IMessageFilter filter) at the beginning of your program.
The IMessageFilter interface has just one method:
bool PreFilterMessage(ref Message m);
That is called for every message handled by the application. There you can use m.HWnd to identify the different windows of your program.
I've made an extension inside a package and I am calling the following code (occurs when a user presses a button in the toolbar):
DocumentEvents documentEvents = (DTE2)GetService(typeof(DTE));
_dte.Events.DebuggerEvents.OnEnterBreakMode += DebuggerEvents_OnEnterBreakMode;
_dte.Events.DebuggerEvents.OnEnterDesignMode += DebuggerEvents_OnEnterDesignMode;
_dte.Events.DebuggerEvents.OnContextChanged += DebuggerEvents_OnContextChanged;
_dte.Events.DocumentEvents.DocumentSaved += new _dispDocumentEvents_DocumentSavedEventHandler(DocumentEvents_DocumentSaved);
_dte.Events.DocumentEvents.DocumentOpened += new _dispDocumentEvents_DocumentOpenedEventHandler(DocumentEvents_DocumentOpened);
void DocumentEvents_DocumentOpened(Document Document)
{
}
void DocumentEvents_DocumentSaved(Document Document)
{
}
void DebuggerEvents_OnEnterBreakMode(dbgEventReason Reason, ref dbgExecutionAction ExecutionAction)
{
}
void DebuggerEvents_OnContextChanged(Process NewProcess, Program NewProgram, Thread NewThread, StackFrame NewStackFrame)
{
}
private void DebuggerEvents_OnEnterDesignMode(dbgEventReason reason)
{
}
The first and the major problem is that the subscription to the event doesn't work. I've tried:
Opening new documents
Detaching from debug (thus supposedly triggering OnEnterDesignMode
Saving a document
None of these seem to have any effect and the callback functions were never called.
The second issue is that the subscription to the event line works USUALLY (the subscription itself, the callback doesn't work as described above) but after a while running the subscription line, e.g:
_dte.Events.DebuggerEvents.OnEnterBreakMode -= DebuggerEvents_OnEnterBreakMode;
Causes an exception:
Exception occured!
System.Runtime.InteropServices.InvalidComObjectException: COM object that has been separated from its underlying RCW cannot be used.
at System.StubHelpers.StubHelpers.StubRegisterRCW(Object pThis, IntPtr pThread)
at System.Runtime.InteropServices.UCOMIConnectionPoint.Unadvise(Int32 dwCookie)
at EnvDTE._dispDebuggerEvents_EventProvider.remove_OnEnterDesignMode(_dispDebuggerEvents_OnEnterDesignModeEventHandler A_1)
Any ideas will be welcome
Thanks!
Vitaly
Posting an answer that I got from MSDN forums, by Ryan Molden, in case it helps anyone:
I believe the problem here is how the
CLR handles COM endpoints (event
sinks). If I recall correctly when
you hit the
_applicationObject.Events.DebuggerEvents
part of your 'chain' the CLR will
create a NEW DebuggerEvents object for
the property access and WON'T cache
it, therefor it comes back to you, you
sign up an event handler to it (which
creates a strong ref between the
TEMPORARY object and your object due
to the delegate, but NOT from your
object to the temporary object, which
would prevent the GC). Then you don't
store that object anywhere so it is
immediately GC eligible and will
eventually be GC'ed.
I changed the code to store DebuggerEvents as a field and it all started to work fine.
Here is what #VitalyB means using code:
// list where we will place events.
// make sure that this variable is on global scope so that GC does not delete the evvents
List<object> events = new List<object>();
public void AddEvents(EnvDTE dte)
{
// create an event when a document is open
var docEvent = dte.Events.DocumentEvents;
// add event to list so that GC does not remove it
events.Add(docEvent );
docEvent.DocumentOpened += (document)=>{
Console.Write("document was opened!");
};
// you may add more events:
var commandEvent = dte.Events.CommandEvents;
events.Add(commandEvent );
commandEvent.AfterExecute+= etc...
}