public class VideoView extends android.widget.VideoView {
    /**
     * Android系统在更加xml布局找这个类，并且实例化的时候，用该构造方法实例化
     *
     * @param context
     * @param attrs
     */
    public VideoView(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    public VideoView(Context context) {
        super(context);
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
//        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        setMeasuredDimension(widthMeasureSpec, heightMeasureSpec);
    }

    /**
     * 设置视频画面的宽和高
     * @param videoWidth
     * @param videoHeight
     */
    public void setVideoSize(int videoWidth, int videoHeight) {
        ViewGroup.LayoutParams layoutParams  =getLayoutParams();
        layoutParams.width = videoWidth;
        layoutParams.height = videoHeight;
        setLayoutParams(layoutParams);
    }

}

wm = (WindowManager) getSystemService(WINDOW_SERVICE);
screenWidth = wm.getDefaultDisplay().getWidth();
screenHeight = wm.getDefaultDisplay().getHeight();

DisplayMetrics displayMetrics = new DisplayMetrics();
this.getWindowManager().getDefaultDisplay().getMetrics(displayMetrics);
screenWidth = displayMetrics.widthPixels;
screenHeight = displayMetrics.heightPixels;

/**
 * true全屏
 * flase默认
*/
private boolean isFullScreen = false;

/**
 *  视频全屏和默认
 *  @param type
*/
public void setVideoType(int type){
	switch (type) {
		case SCREEN_FULL:
			videoview.setVideoSize(screenWidth, screenHeight);
			isFullScreen = true;
			btn_switch_screen.setBackgroundResource(R.drawable.btn_screen_dafult_selector);
			break;

		case SCREEN_DEFULT:
			//视频的宽
			int mVideoWidth = videoWidth;
			//视频的高
			int mVideoHeight = videoHeight;
			//屏幕的宽
			int width = screenWidth;
			//屏幕的宽
			int height = screenHeight;
			if (mVideoWidth > 0 && mVideoHeight > 0) {
				if ( mVideoWidth * height  > width * mVideoHeight ) {
					//Log.i("@@@", "image too tall, correcting");
					height = width * mVideoHeight / mVideoWidth;
				} else if ( mVideoWidth * height  < width * mVideoHeight ) {
					//Log.i("@@@", "image too wide, correcting");
					width = height * mVideoWidth / mVideoHeight;
				} else {
					//Log.i("@@@", "aspect ratio is correct: " +
					//width+"/"+height+"="+
					//mVideoWidth+"/"+mVideoHeight);
				}
			}
			videoview.setVideoSize(width, height);
			btn_switch_screen.setBackgroundResource(R.drawable.btn_screen_full_selector);
			isFullScreen = false;
			
			break;
    }

}

//设置屏幕不锁屏
getWindow().setFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON, WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON);

case R.id.btn_switch_screen:
	if(isFullScreen){
	   setVideoType(SCREEN_DEFUALT);
	}else{
	   setVideoType(SCREEN_FULL);
	}
break