沉浸模式（支持4.4以上版本）

一：//沉浸模式

public class ViewHelper {

    private View decorView;

     public ViewHelper(View decorView){
         this.decorView=decorView;
     }

     public ViewHelper(){

     }


    /**
     * 隐藏 虚拟按钮的 线程
     */
     Runnable hideNavigationRunable=new Runnable() {
         @Override
         public void run() {
               UiUtils.hideNavigation(decorView);
         }
     };

    public void  hideNavigation( Activity activity){
        boolean hasNavigation=UiUtils.hasNavigationBar(activity);
        if(hasNavigation&& Build.VERSION.SDK_INT>=Build.VERSION_CODES.KITKAT){
            final View decorView = activity.getWindow().getDecorView();

            UiUtils.hideNavigation(decorView);
            decorView.setOnSystemUiVisibilityChangeListener(new View.OnSystemUiVisibilityChangeListener() {
                @Override
                public void onSystemUiVisibilityChange(int visibility) {

                    if ((visibility & View.SYSTEM_UI_FLAG_HIDE_NAVIGATION) == 0) {

                        Handler h = decorView.getHandler();
                        if (h != null) {
                            h.removeCallbacks(hideNavigationRunable);
                            h.postDelayed(hideNavigationRunable, 2000);
                        }
                }}
            });
        }

    }
}

二：调用

//沉浸模式
 viewHelper=new ViewHelper(getWindow().getDecorView());
 viewHelper.hideNavigation(this);