Update ChatActivity.java

app/src/main/java/com/electric/chargingpile/activity/ChatActivity.java

        if (chatFragment == null) {
            chatFragment = ChatFragment.newInstance(position - 1);
            fragmentManager.beginTransaction().add(R.id.fragment_container, chatFragment).commit();
            chatFragment.setMenuVisibility(true);
        }
    }
    private void removeChatFragment() {
        setFullScreen(false);
        setStatusBarVisibility(false);
        fragmentContainer.setVisibility(View.GONE);
        FragmentManager fragmentManager = getSupportFragmentManager();
        if (chatFragment != null) {
            fragmentManager.beginTransaction().remove(chatFragment).commit();
            chatFragment.setMenuVisibility(false);
        }
        chatFragment = null;
    }
    /**
    @Override
    public boolean onKeyDown(int keyCode, KeyEvent event) {
        if (keyCode == KeyEvent.KEYCODE_BACK && event.getAction() == KeyEvent.ACTION_DOWN) {
            if (chatFragment != null) {
                removeChatFragment();
                return false;
            }
            if ((System.currentTimeMillis() - exitTime) > 2000) {
                Toast.makeText(getApplicationContext(), "再按一次退出程序", Toast.LENGTH_SHORT).show();
                exitTime = System.currentTimeMillis();