Hi all developers,
I wrote a native code wrapper for a library that manages Zip files
https://github.com/srikanth-lingala/zip4j
https://jar-download.com/artifacts/net.lingala.zip4j/zip4j/2.6.1/documentation
This library permit to do some interesting things with Zip files.
The wrapper I wrote seem to work well, but the only problem I had is that it blocks the main thread while do operations on Zip files.
This is not a big problem with small files, but is a real problem with large files where the main thread is blocked, I cannot raise
events on main thread to log the operation progress, change a value of a progressbar etc.
The library has _Progress event, this is fired on the Main thread, the user can print it on the log, set a progressbar value etc...
this currently happen but only when operation on files is done.
On library every command can thrown an exception and return a boolean value to inform the user if operation was successfully completed or error occoured.
So the user can do eg, something like this:
I searched on the forum and found this good tutorial by Erel:
https://www.b4x.com/android/forum/threads/java-libraries-and-multithreading.12697/#content
I managed it to work in background using a Runnable as Erel suggested, the problem here is that Runnable cannot return a value, it's signature is 'void' and it cannot thrown an exception I catch with try-catch.
Searching on the web I found that a better solution is to use Callable, so I've read #post2 in the same Erel thread:
I do not yet tried it, but the problem is that as Erel said on same thread, it can only return the value when the task completes:
What I want is to return a boolean value from functions and even the _Error event where I pass the message string of exception occoured.
Naturally even raise _Progress event....
Because I'm not very Java expert I accept any suggestion to solve this, here I post just a function that use this mechanism, but my library
has 12 of these that I need to change to work the right way.
Any suggestion appreciated
Many Thanks
Max
I wrote a native code wrapper for a library that manages Zip files
https://github.com/srikanth-lingala/zip4j
https://jar-download.com/artifacts/net.lingala.zip4j/zip4j/2.6.1/documentation
This library permit to do some interesting things with Zip files.
The wrapper I wrote seem to work well, but the only problem I had is that it blocks the main thread while do operations on Zip files.
This is not a big problem with small files, but is a real problem with large files where the main thread is blocked, I cannot raise
events on main thread to log the operation progress, change a value of a progressbar etc.
The library has _Progress event, this is fired on the Main thread, the user can print it on the log, set a progressbar value etc...
this currently happen but only when operation on files is done.
Events:
@Events(values={"Progress (Method As String, Percent As Int, Complete As Boolean)", "Error (Method As String, Error As String)"})On library every command can thrown an exception and return a boolean value to inform the user if operation was successfully completed or error occoured.
So the user can do eg, something like this:
B4X:
Dim Success = Zip.ExtractZip(..., ..., ...)
If Success Then
... open here an extracted file
End IfI searched on the forum and found this good tutorial by Erel:
https://www.b4x.com/android/forum/threads/java-libraries-and-multithreading.12697/#content
I managed it to work in background using a Runnable as Erel suggested, the problem here is that Runnable cannot return a value, it's signature is 'void' and it cannot thrown an exception I catch with try-catch.
Searching on the web I found that a better solution is to use Callable, so I've read #post2 in the same Erel thread:
Java:
public static void runAsync(final BA ba, final Object Sender, String FullEventName,
final Object[] errorResult, final Callable<Object[]> callable)
public void Initialize(String Dir, String FileName) throws IOException, BiffException {
InputStream in = File.OpenInput(Dir, FileName).getObject();
Workbook w = Workbook.getWorkbook(in, getDefaultSettings(Encoding));
in.close();
setObject(w);
}
public void InitializeAsync(BA ba, String EventName, final String Dir, final String FileName) {
BA.runAsync(ba, this, EventName + "_ready", new Object[] {false}, new Callable<Object[]>() {
@Override
public Object[] call() throws Exception {
Initialize(Dir, FileName);
return new Object[] {true};
}
});
}I do not yet tried it, but the problem is that as Erel said on same thread, it can only return the value when the task completes:
... so the problem here seem to be I cannot anyway raise the _Progress event in the middle.
What I want is to return a boolean value from functions and even the _Error event where I pass the message string of exception occoured.
Naturally even raise _Progress event....
Because I'm not very Java expert I accept any suggestion to solve this, here I post just a function that use this mechanism, but my library
has 12 of these that I need to change to work the right way.
Any suggestion appreciated
Many Thanks
Max
Original blocking function:
public boolean ExtractZip(final String ZipPath, final String DestFolder, final String Password) {
// Initiate ZipFile object with the path/name of the zip file.
ZipFile zipFile = new ZipFile(ZipPath);
final String evt = eventName + "_progress";
final String errEvt = eventName + "_error";
final int Percent, oldPercent;
try {
Percent = 0; oldPercent = 0;
// Set true to monitor progress state
// This work on different thread
zipFile.setRunInThread(true);
// Check to see if the zip file is password protected
if (Password.length() > 0) {
try {
// If yes, then set the password for the zip file
zipFile.setPassword(Password.toCharArray());
} catch (Exception e) {
BA.Log("Zip4j: ExtractZip -> Cannot set Password for file " + ZipPath);
if (ba.subExists(errEvt)) {
ba.raiseEvent(this, errEvt, "ExtractZip", "Cannot set Password for file " + ZipPath);
}
return false;
}
}
// Extracts all files to the path specified
zipFile.extractAll(DestFolder);
// Get progress
if (ba.subExists(evt)) {
ProgressMonitor progressMonitor = zipFile.getProgressMonitor();
while (progressMonitor.getState().equals(ProgressMonitor.State.BUSY)) { // New syntax
//BA.Log("Extracting. Percent done: " + progressMonitor.getPercentDone());
Percent = progressMonitor.getPercentDone();
if (oldPercent != Percent) {
//BA.Log("Zip4j: RAISE EVENT: " + evt);
ba.raiseEvent(this, evt, "ExtractZip", Percent, false);
}
oldPercent = Percent;
}
// HERE OPERATION IS DONE
BA.Log("Zip4j: ExtractZip -> Done extracted content of file " + ZipPath +
" into Folder " + DestFolder + " Result: " + getResultString(progressMonitor.getResult()));
ba.raiseEvent(this, evt, "ExtractZip", 100, true);
} else {
BA.Log("Zip4j: ExtractZip -> Sub " + OriginalEventName +
"_Progress does not exists. Use Async Mode to extract file " + ZipPath +
" into Folder " + DestFolder);
}
return true;
} catch (ZipException e) {
String err = e.getMessage().replace("net.lingala.zip4j.exception.ZipException: net.lingala.zip4j.exception.ZipException: ", "");
err = err.replaceAll(":", "");
//BA.Log("Zip4j: ExtractZip -> " + err);
if (ba.subExists(errEvt)) {
ba.raiseEvent(this, errEvt, "ExtractZip", err);
}
return false;
} finally {
try {
zipFile.close();
} catch (IOException e) {
e.printStackTrace();
if (ba.subExists(errEvt)) {
ba.raiseEvent(this, errEvt, "ExtractZip", e.getMessage());
}
return false;
};
}
}
Unblocking. But cannot return value:
public void ExtractZip(final String ZipPath, final String DestFolder, final String Password) {
Runnable r = new Runnable() {
@Override
public void run() {
// Initiate ZipFile object with the path/name of the zip file.
ZipFile zipFile = new ZipFile(ZipPath);
final String evt = eventName + "_progress";
final String errEvt = eventName + "_error";
final int Percent, oldPercent;
try {
Percent = 0; oldPercent = 0;
// Set true to monitor progress state
// Work on background thread
zipFile.setRunInThread(true);
// Set if the zip file is password protected
if (Password.length() > 0) {
try {
// if yes, then set the password for the zip file
zipFile.setPassword(Password.toCharArray());
} catch (Exception e) {
BA.Log("Zip4j: ExtractZip -> Cannot set Password for file " + ZipPath);
if (ba.subExists(errEvt)) {
ba.raiseEventFromDifferentThread(this, null, 0, errEvt, false,
new Object[] {"ExtractZip", "Cannot set Password for file " + ZipPath});
}
return;
}
}
// Extracts all files to the path specified
zipFile.extractAll(DestFolder);
// Get progress
if (ba.subExists(evt)) {
ProgressMonitor progressMonitor = zipFile.getProgressMonitor();
while (progressMonitor.getState().equals(ProgressMonitor.State.BUSY)) {
//BA.Log("Extracting. Percent done: " + progressMonitor.getPercentDone());
Percent = progressMonitor.getPercentDone();
if (oldPercent != Percent) {
//BA.Log("Zip4j: RAISE EVENT: " + evt);
ba.raiseEventFromDifferentThread(this, null, 0, evt, false, new Object[] {"ExtractZip", Percent, false});
}
oldPercent = Percent;
}
// HERE OPERATION IS DONE
BA.Log("Zip4j: ExtractZip -> Done extracted content of file " + ZipPath +
" into Folder " + DestFolder + " Result: " + getResultString(progressMonitor.getResult()));
BA.Log("Zip4j: RAISE FINAL EVENT: " + evt);
ba.raiseEventFromDifferentThread(this, null, 0, evt, false, new Object[] {"ExtractZip", 100, true});
} else {
BA.Log("Zip4j: ExtractZip -> Sub " + OriginalEventName +
"_Progress does not exists. Use Async Mode to extract file " + ZipPath +
" into Folder " + DestFolder);
}
return;
} catch (ZipException e) {
String err = e.getMessage().replace("net.lingala.zip4j.exception.ZipException: net.lingala.zip4j.exception.ZipException: ", "");
err = err.replaceAll(":", "");
//BA.Log("Zip4j: ExtractZip -> " + err);
if (ba.subExists(errEvt)) {
ba.raiseEventFromDifferentThread(this, null, 0, errEvt, false, new Object[] {"ExtractZip", err});
}
return;
} finally {
try {
zipFile.close();
} catch (IOException e) {
e.printStackTrace();
if (ba.subExists(errEvt)) {
ba.raiseEventFromDifferentThread(this, null, 0, errEvt, false, new Object[] {"ExtractZip", e.getMessage()});
}
return;
};
}
}
};
BA.submitRunnable(r, this, 0);
}
Last edited:
