1. A computing device, comprising: a touch-sensitive display; a processor; memory; and one or more programs, wherein the one or more programs are stored in the memory and configured to be executed by the processor, the one or more programs including instructions for: playing-back a video file on the touch-sensitive display; displaying a play progress bar on the touch-sensitive display, the play progress bar including a timeline indicating a time span of the video file being played; detecting two touch points making initial contact at respective initial positions on the play progress bar; detecting the two touch points moving away from each other on the play progress bar; and, in response to detecting the two touch points moving away from each other on the play progress bar: expanding a portion of the play progress bar in accordance with the movement of the two touch points, wherein the portion of the play progress bar that is expanded is determined by the respective initial positions of the two touch points; and contracting a part of the play progress bar outside the expanded portion.