JUCEApplicationBase Class Reference

Abstract base class for application classes. More...

#include <juce_ApplicationBase.h>

Inheritance diagram for JUCEApplicationBase:

Public Member Functions
virtual	~JUCEApplicationBase ()
	Destructor.
virtual const String	getApplicationName ()=0
	Returns the application's name.
virtual const String	getApplicationVersion ()=0
	Returns the application's version number.
virtual bool	moreThanOneInstanceAllowed ()=0
	Checks whether multiple instances of the app are allowed.
virtual void	initialise (const String &commandLineParameters)=0
	Called when the application starts.
virtual void	shutdown ()=0
virtual void	anotherInstanceStarted (const String &commandLine)=0
	Indicates that the user has tried to start up another instance of the app.
virtual void	systemRequestedQuit ()=0
	Called when the operating system is trying to close the application.
virtual void	suspended ()=0
	This method is called when the application is being put into background mode by the operating system.
virtual void	resumed ()=0
	This method is called when the application is being woken from background mode by the operating system.
virtual void	unhandledException (const std::exception *, const String &sourceFilename, int lineNumber)=0
	If any unhandled exceptions make it through to the message dispatch loop, this callback will be triggered, in case you want to log them or do some other type of error-handling.
virtual void	memoryWarningReceived ()
	Called by the operating system to indicate that you should reduce your memory footprint.
virtual bool	backButtonPressed ()
	This will be called when the back button on a device is pressed.
void	setApplicationReturnValue (int newReturnValue) noexcept
	Sets the value that should be returned as the application's exit code when the app quits.
int	getApplicationReturnValue () const noexcept
	Returns the value that has been set as the application's exit code.
bool	isInitialising () const noexcept
	Returns true if the application hasn't yet completed its initialise() method and entered the main event loop.

Static Public Member Functions
static JUCEApplicationBase *	getInstance () noexcept
	Returns the global instance of the application object that's running.
static void	quit ()
	Signals that the main message loop should stop and the application should terminate.
static StringArray JUCE_CALLTYPE	getCommandLineParameterArray ()
	Returns the application's command line parameters as a set of strings.
static String JUCE_CALLTYPE	getCommandLineParameters ()
	Returns the application's command line parameters as a single string.
static bool	isStandaloneApp () noexcept
	Returns true if this executable is running as an app (as opposed to being a plugin or other kind of shared library.

Protected Member Functions
	JUCEApplicationBase ()

Detailed Description

Abstract base class for application classes.

Note that in the juce_gui_basics module, there's a utility class JUCEApplication which derives from JUCEApplicationBase, and takes care of a few chores. Most of the time you'll want to derive your class from JUCEApplication rather than using JUCEApplicationBase directly, but if you're not using the juce_gui_basics module then you might need to go straight to this base class.

Any application that wants to run an event loop must declare a subclass of JUCEApplicationBase, and implement its various pure virtual methods.

It then needs to use the START_JUCE_APPLICATION macro somewhere in a CPP file to declare an instance of this class and generate suitable platform-specific boilerplate code to launch the app.

e.g.

class MyJUCEApp  : public JUCEApplication
{
public:
    MyJUCEApp()  {}
    ~MyJUCEApp() {}
 
    void initialise (const String& commandLine) override
    {
        myMainWindow.reset (new MyApplicationWindow());
        myMainWindow->setBounds (100, 100, 400, 500);
        myMainWindow->setVisible (true);
    }
 
    void shutdown() override
    {
        myMainWindow = nullptr;
    }
 
    const String getApplicationName() override
    {
        return "Super JUCE-o-matic";
    }
 
    const String getApplicationVersion() override
    {
        return "1.0";
    }
 
private:
    std::unique_ptr<MyApplicationWindow> myMainWindow;
};
 
// this generates boilerplate code to launch our app class:
START_JUCE_APPLICATION (MyJUCEApp)

See also

JUCEApplication, START_JUCE_APPLICATION

Constructor & Destructor Documentation

JUCEApplicationBase()

JUCEApplicationBase::JUCEApplicationBase ( )

protected

~JUCEApplicationBase()

virtual JUCEApplicationBase::~JUCEApplicationBase ( )

virtual

Destructor.

Member Function Documentation

getInstance()

static JUCEApplicationBase * JUCEApplicationBase::getInstance ( )

staticnoexcept

Returns the global instance of the application object that's running.

getApplicationName()

virtual const String JUCEApplicationBase::getApplicationName ( )

pure virtual

Returns the application's name.

Implemented in JUCEApplication.

getApplicationVersion()

virtual const String JUCEApplicationBase::getApplicationVersion ( )

pure virtual

Returns the application's version number.

Implemented in JUCEApplication.

moreThanOneInstanceAllowed()

virtual bool JUCEApplicationBase::moreThanOneInstanceAllowed ( )

pure virtual

Checks whether multiple instances of the app are allowed.

If your application class returns true for this, more than one instance is permitted to run (except on the Mac where this isn't possible).

If it's false, the second instance won't start, but you will still get a callback to anotherInstanceStarted() to tell you about this - which gives you a chance to react to what the user was trying to do.

See also

anotherInstanceStarted

Implemented in JUCEApplication.

initialise()

virtual void JUCEApplicationBase::initialise ( const String & commandLineParameters )

pure virtual

Called when the application starts.

This will be called once to let the application do whatever initialisation it needs, create its windows, etc.

After the method returns, the normal event-dispatch loop will be run, until the quit() method is called, at which point the shutdown() method will be called to let the application clear up anything it needs to delete.

If during the initialise() method, the application decides not to start-up after all, it can just call the quit() method and the event loop won't be run.

Parameters

commandLineParameters

the line passed in does not include the name of the executable, just the parameter list. To get the parameters as an array, you can call JUCEApplication::getCommandLineParameters()

See also

shutdown, quit

shutdown()

virtual void JUCEApplicationBase::shutdown ( )

pure virtual

anotherInstanceStarted()

virtual void JUCEApplicationBase::anotherInstanceStarted ( const String & commandLine )

pure virtual

Indicates that the user has tried to start up another instance of the app.

This will get called even if moreThanOneInstanceAllowed() is false. It is currently only implemented on Windows and Mac.

See also

moreThanOneInstanceAllowed

Implemented in JUCEApplication.

systemRequestedQuit()

virtual void JUCEApplicationBase::systemRequestedQuit ( )

pure virtual

Called when the operating system is trying to close the application.

The default implementation of this method is to call quit(), but it may be overloaded to ignore the request or do some other special behaviour instead. For example, you might want to offer the user the chance to save their changes before quitting, and give them the chance to cancel.

If you want to send a quit signal to your app, this is the correct method to call, because it means that requests that come from the system get handled in the same way as those from your own application code. So e.g. you'd call this method from a "quit" item on a menu bar.

Implemented in JUCEApplication.

suspended()

virtual void JUCEApplicationBase::suspended ( )

pure virtual

This method is called when the application is being put into background mode by the operating system.

Implemented in JUCEApplication.

resumed()

virtual void JUCEApplicationBase::resumed ( )

pure virtual

This method is called when the application is being woken from background mode by the operating system.

Implemented in JUCEApplication.

unhandledException()

virtual void JUCEApplicationBase::unhandledException ( const std::exception * , const String & sourceFilename, int lineNumber )

pure virtual

If any unhandled exceptions make it through to the message dispatch loop, this callback will be triggered, in case you want to log them or do some other type of error-handling.

If the type of exception is derived from the std::exception class, the pointer passed-in will be valid. If the exception is of unknown type, this pointer will be null.

Implemented in JUCEApplication.

memoryWarningReceived()

virtual void JUCEApplicationBase::memoryWarningReceived ( )

virtual

Called by the operating system to indicate that you should reduce your memory footprint.

You should override this method to free up some memory gracefully, if possible, otherwise the host may forcibly kill your app.

At the moment this method is only called on iOS.

References jassertfalse.

backButtonPressed()

virtual bool JUCEApplicationBase::backButtonPressed ( )

virtual

This will be called when the back button on a device is pressed.

The return value should be used to indicate whether the back button event has been handled by the application, for example if you want to implement custom navigation instead of the standard behaviour on Android.

This is currently only implemented on Android devices.

Returns

true if the event has been handled, or false if the default OS behaviour should happen

quit()

static void JUCEApplicationBase::quit ( )

static

Signals that the main message loop should stop and the application should terminate.

This isn't synchronous, it just posts a quit message to the main queue, and when this message arrives, the message loop will stop, the shutdown() method will be called, and the app will exit.

Note that this will cause an unconditional quit to happen, so if you need an extra level before this, e.g. to give the user the chance to save their work and maybe cancel the quit, you'll need to handle this in the systemRequestedQuit() method - see that method's help for more info.

See also

MessageManager

Referenced by StandaloneFilterWindow::closeButtonPressed().

getCommandLineParameterArray()

static StringArray JUCE_CALLTYPE JUCEApplicationBase::getCommandLineParameterArray ( )

static

Returns the application's command line parameters as a set of strings.

See also

getCommandLineParameters

getCommandLineParameters()

static String JUCE_CALLTYPE JUCEApplicationBase::getCommandLineParameters ( )

static

Returns the application's command line parameters as a single string.

See also

getCommandLineParameterArray

setApplicationReturnValue()

void JUCEApplicationBase::setApplicationReturnValue ( int newReturnValue )

noexcept

Sets the value that should be returned as the application's exit code when the app quits.

This is the value that's returned by the main() function. Normally you'd leave this as 0 unless you want to indicate an error code.

See also

getApplicationReturnValue

getApplicationReturnValue()

int JUCEApplicationBase::getApplicationReturnValue ( ) const

noexcept

Returns the value that has been set as the application's exit code.

See also

setApplicationReturnValue

isStandaloneApp()

static bool JUCEApplicationBase::isStandaloneApp ( )

staticnoexcept

Returns true if this executable is running as an app (as opposed to being a plugin or other kind of shared library.

isInitialising()

bool JUCEApplicationBase::isInitialising ( ) const

noexcept

Returns true if the application hasn't yet completed its initialise() method and entered the main event loop.

This is handy for things like splash screens to know when the app's up-and-running properly.

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The documentation for this class was generated from the following file:

• juce_ApplicationBase.h