试了很多种方法，只有这种满屏效果最好。
if(Build.VERSION.SDK_INT >= Build.VERSION_CODES.P) {WindowManager.LayoutParams lp = getWindow().getAttributes();lp.layoutInDisplayCutoutMode = WindowManager.LayoutParams.LAYOUT_IN_DISPLAY_CUTOUT_MODE_SHORT_EDGES;getWindow().setAttributes(lp);
}else{getWindow().requestFeature(Window.FEATURE_NO_TITLE);getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, WindowManager.LayoutParams.FLAG_FULLSCREEN);
}
final View decorView = getWindow().getDecorView();
decorView.setSystemUiVisibility(View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN | View.SYSTEM_UI_FLAG_LAYOUT_STABLE | View.SYSTEM_UI_FLAG_HIDE_NAVIGATION);

View.SYSTEM_UI_FLAG_HIDE_NAVIGATION用来隐藏底部悬浮条，WindowManager.LayoutParams.LAYOUT_IN_DISPLAY_CUTOUT_MODE_SHORT_EDGES用来在android高版本满屏，穿过摄像头。