从片段NullPointerException异常调用活动的方法 [英] Calling activity method from fragment NullPointerException

问题描述

我有一个从片段访问活动的方法的问题。 或任何诠释从该片段的活性。

I have a problem with accessing activity's method from fragment. Or anything int the activity from the fragment.

下面是片段code：

public class MainFragment extends Fragment {

private MainActivity ma = (MainActivity) getActivity();
public SipAudioCall call = null;
public SipManager mSipManager = null;
public SipProfile mSipProfile = null;



public MainFragment() {
    // TODO Auto-generated constructor stub

}

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState) {
    // Create a new TextView and set its text to the fragment's section
    // number argument value.
    LinearLayout mLinearLayout = (LinearLayout) inflater.inflate(R.layout.main_layout, container, false);

    final Button callbtn = (Button) mLinearLayout.findViewById(R.id.callbtn);
    final Button endbtn = (Button) mLinearLayout.findViewById(R.id.endbtn);



    callbtn.setOnClickListener(new View.OnClickListener() {
        public void onClick(View v) {
            callbtn.setVisibility(View.GONE);
            endbtn.setVisibility(View.VISIBLE);
            ma.initiateCall();    
        }
    });

也许铸造的活动是错了吗？ THX提前

Maybe casting the activity is wrong? Thx in advance

推荐答案

我猜的片段没有连接到活动当u调用getActivity（）。尝试初始化片段的方法onAttach活动参考（）。

I'm guessing that the fragment is not attached to the activity when u call getActivity(). Try to initialize the activity reference in the fragment method onAttach().

因此​​，像这样：

@Override
    public void onAttach(Activity activity) {
        super.onAttach(activity);
        try {
            ma = (MainActivity) activity;
        } catch (ClassCastException e) {
            throw new ClassCastException(activity.toString() + " Not MainActivity class instance");
        }
    }

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