那些类

DispalayMetrics A structure describing general information about a display, such as its size, density, and font scaling.

LongSparseArray SparseArray mapping longs to Objects. Unlike a normal array of Objects, there can be gaps in the indices. It is intended to be more efficient than using a HashMap to map Longs to Objects.

ViewOverLay The view's overlay layer. Developers get a reference to the overlay via getOverlay() and add/remove objects to/from the overlay directly through the Overlay methods.

MedioRecorder``

AudioRecord``

ActivityCompat``

PackageManager``

MediaPlayer``

MediaTrack``