拖动条用SeekBar表示，与进度条类似，只是增加量一个可拖动的滑块。用户可以通过拖动来改变值，通常用于对数值的调节。(The drag bar is represented by SeekBar, similar to the progress bar, but only by adding a drag slider. Users can change values by dragging, which is usually used to adjust values.)