iPhone Open Application Development

Progress Indicators

Progress indicators notify the user that an operation is in progress. There are two types of indicators supported in UIKit:

UIProgressIndicator

This class presents a spinning clock-like animation—the kind seen when turning on the iPhone's WiFi or Bluetooth support, or when your Mac desktop boots up.

UIProgressBar

This class provides a thermometer-like readout, allowing the application to express how far along an operation is before completion.

Both types of indicators are derived from the UIView base class, meaning they can be layered on top of text views, alert sheets, most types of table cells, and any other object that derives from UIView.

UIProgressIndicator: Things That Spin

The UIProgressIndicator class is a simple animation class small enough to attach to nearly any UIView object, including table cells and alert sheets. The indicator displays a clock-like animation of tick marks making revolutions around a circle.

The indicator is created with a frame identifying the indicator's size and the coordinates relative to the view to which it is attached.

UIProgressIndicator *progressView = [ UIProgressIndicator alloc ]
    initWithFrame: CGRectMake(0, 0, 32, 32) ];

The indicator supports two styles, white (0) and dark gray (1), which are useful depending on the type of object they are being attached to. The style is set by invoking the object's setStyle method:

[ progressView setStyle: 0 ];

Use the setAnimationDuration method to adjust the amount of time it takes for one ...