Android - What is a secondary progress in ProgressBar?

Anyone know about the detail? Any we开发者_如何转开发bsite or suggestion?

From the source:

There is also a secondary progress displayable on a progress bar which is useful for displaying intermediate progress, such as the buffer level during a streaming playback progress bar.

One can find a fully worked example of displaying such a bar, including screenshots of the appearance of such a bar in a particular style (circular bar which fills from the bottom):

In the image above, the secondary bar is the green area, when it reaches the top, some subtask is complete.

Secondary progress vs Progress can be thought of like the downloaded part of a video you're watching vs the complete length of the progress bar