在Fragment

Question

你好我试图添加一个按钮，但我一直收到这个错误： java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.LinearLayout.addView(android.view.View, android.view.ViewGroup$LayoutParams)' on a null object reference

这是我的代码，它在常规活动中运行良好，它不作为片段工作：

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    View v = inflater.inflate(R.layout.fav, container, false);

    lSecond = (LinearLayout) v.findViewById(R.id.lSecond);
    lThird = (LinearLayout) v.findViewById(R.id.lThird);
    return v;
}
 public void bCreate(String i)
{
    LinearLayout.LayoutParams btnParams = new LinearLayout.LayoutParams(matchParent, wrapContent);
    Button btnNew = new Button(this.getActivity());
    btnNew.setBackgroundResource(R.drawable.button);
    btnNew.setTextColor(Color.parseColor("#ffffff"));
    btnNew.setText(i);
    scale =  getResources().getDisplayMetrics().density;
    int top = (int) (5 * scale + 0.5f);
    int bot = (int) (5 * scale + 0.5f);
    if (Second < Third)
    {
        int left = (int) (10 * scale + 0.5f);
        int right = (int) (5 * scale + 0.5f);
        btnParams.leftMargin = left;
        btnParams.rightMargin = right;
        btnParams.topMargin = top;
        btnParams.bottomMargin = bot;
        lSecond.addView(btnNew, btnParams);
        Second++;
        btnNew.setOnClickListener(listen);
    }

bCreate在onCreate中被调用，而String i - 是来自数据库的字符串

Answer 1

bCreate()过早被召唤。您尝试在具有值之前访问lSecond。在返回之前在bCreate()中致电onCreateView()。