iPhone Open Application Development

Celestial

Celestial is the preferred iPhone framework for playing sound and music files and recording sound from the built-in microphone. Celestial uses an AVController class to play sound samples, which are represented as AVItem objects. The framework also supports an optional AVQueue class to arrange playback of different samples.

What Celestial is not useful for is playing a digital stream; that is, a raw output channel of sound. That will be covered in the next section on the Audio Toolbox. Celestial works only with audio files.

To tap into Celestial, your application must be linked to the Celestial framework. Using the tool chain, link Celestial to your application by adding the following arguments to the compiler arguments described in Chapter 2:

$ arm-apple-darwin-gcc -o MyApp MyApp.m -lobjc \
    -framework CoreFoundation \
    -framework Foundation \
    -framework Celestial

To add this option to the sample makefile from Chapter 2, add the Celestial framework to the linker flags section so that the library is linked in:

LDFLAGS =    -lobjc \
        -framework CoreFoundation \
        -framework Foundation \
        -framework Celestial

ringerState

Playing sounds can be very useful for many types of applications, but it's up to the developer to ensure that the user's desire to silence her phone is respected. Before a sound is played, you should first check the ringer state—the mute switch on the side of the phone. To check this, UIKit provides a method named ringerState within the UIHardware class.

int ringerState ...