通过位移动画移动一个控件后，控件消失不见了

Question

@Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        RelativeLayout rl_Root = new RelativeLayout(this);
        RelativeLayout.LayoutParams lp = new RelativeLayout.LayoutParams(RelativeLayout.LayoutParams.MATCH_PARENT, RelativeLayout.LayoutParams.MATCH_PARENT);
        addContentView(rl_Root, lp);

        Button btn_Test = new Button(this);
        btn_Test.setText("测试");
        rl_Root.addView(btn_Test);

        btn_Test.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                TranslateAnimation animation = new TranslateAnimation(0, 0, 0, 200);
                animation.setInterpolator(new AccelerateInterpolator());
                animation.setDuration(1000);
                animation.setRepeatCount(0);
                animation.setFillAfter(true);
                final Button btn = (Button)v;

                animation.setAnimationListener(new Animation.AnimationListener() {
                    public void onAnimationStart(Animation animation) {}

                    public void onAnimationEnd(Animation animation) {
                        btn.setTop(200);
                    }
                    public void onAnimationRepeat(Animation animation) {}
                });
                btn.startAnimation(animation);
            }
        });
    }

Answer 1

换成了绝对布局也是这样，而且我不用动画移动，直接在OnClick中调用 btn.setTop(200);，按钮也看不见了，说明和TranslateAnimation无关