Question

我有两个可行的应用程序。现在我已经制作了一个新的应用程序，它基本上是一个导航抽屉，我试图将这些其他应用程序分成一个片段。当我尝试调整其中一个应用程序的主要活动代码时，该片段崩溃了。没有警告，没有错误，只是崩溃..

我在这里留下一些片段代码（我正在切割一些线条，我确定这不是问题）：

public class SFragment extends Fragment {
    public SFragment(){}

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {

        View rootView = inflater.inflate(R.layout.fragment_s, container, false);

        rdGroup1 = (RadioGroup)getView().findViewById(R.id.radioGroup1);
        rdGroup2 = (RadioGroup)getView().findViewById(R.id.radioGroup2);
        cBox1 = (CheckBox)getView().findViewById(R.id.especCB);
        button = (Button)getView().findViewById(R.id.button1);
        list = (ListView)getView().findViewById(R.id.listView1);

        return rootView;
    }

        public String itemValue;

        public String[] values;

        private int espec = 0;
        private int curso = 0;
        private int cuatri = 0;

        private ListView list;

        private RadioGroup rdGroup1;
        private RadioGroup rdGroup2;

        private CheckBox cBox1;
        private Button button;

        ArrayAdapter<String> adapter;

        DatabaseHandler db = new DatabaseHandler(getActivity());


    @Override
    public void onActivityCreated(Bundle savedInstanceState) {
        super.onActivityCreated(savedInstanceState);


        String[] values = new String[] {};

        adapter = new ArrayAdapter<String>(getActivity().getApplicationContext(),
                  android.R.layout.simple_list_item_1, android.R.id.text1, values);

        list.setAdapter(adapter); 


        list.setOnItemClickListener(new OnItemClickListener() {

            @Override
            public void onItemClick(AdapterView<?> parent, View view,
               int position, long id) {


                // ListView Clicked item value
                itemValue = (String) list.getItemAtPosition(position);

                // Show Alert 
                Toast.makeText(getActivity(), itemValue, Toast.LENGTH_LONG).show();


                Intent i = new Intent(getActivity().getApplicationContext(), VistaAsig.class);
                i.putExtra("itemValue", itemValue);

                Log.v("MActivity onCreate","onItemClicklist Intent OK");

                startActivity(i);

                Log.v("MActivity onCreate","onItemClicklist Start OK");


            }

            });

        rdGroup1.setOnCheckedChangeListener(new OnCheckedChangeListener(){

            @Override
            public void onCheckedChanged(RadioGroup group, int checkedId) {
                // TODO Auto-generated method stub
                cBox1.setEnabled(true);
                if (checkedId == R.id.radio1){
                    /*No hay especialidades en primero*/
                    curso = 1; cBox1.setEnabled(false);

                }else if (checkedId == R.id.radio2){
                    /*No hay especialidades en segundo*/
                    curso = 2; cBox1.setEnabled(false);
                }else if (checkedId == R.id.radio3){
                    curso = 3;
                }else if (checkedId == R.id.radio4){
                    curso = 4;
                }

                if ((curso != 0)&&(cuatri != 0)) { button.setEnabled(true); }

            }

            });

        rdGroup2.setOnCheckedChangeListener(new OnCheckedChangeListener(){

            @Override
            public void onCheckedChanged(RadioGroup group, int checkedId) {
                // TODO Auto-generated method stub
                if (checkedId == R.id.radio11){
                    cuatri = 1; 
                }else if (checkedId == R.id.radio12){
                    cuatri = 2;
                }

                if ((curso != 0)&&(cuatri != 0)) { button.setEnabled(true); }
            }

        });

        cBox1.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {

            @Override
            public void onCheckedChanged(CompoundButton checkBox, boolean checked) {

             if (espec == 0) espec = 1; else if (espec == 1) espec = 0;
            }
        });

        addData();

    }

Answer 1

在这一行

rdGroup1 = (RadioGroup)getView().findViewById(R.id.radioGroup1);
rdGroup2 = (RadioGroup)getView().findViewById(R.id.radioGroup2);
cBox1 = (CheckBox)getView().findViewById(R.id.especCB);
button = (Button)getView().findViewById(R.id.button1);
list = (ListView)getView().findViewById(R.id.listView1);

将getView()更改为rootView

getView()检索您在onCreateView中返回的视图，但您仍在onCreateView中，因此它返回null，从而导致NullPointerException导致应用崩溃

Answer 2

清理构建然后试试这个：

更改：

adapter = new ArrayAdapter<String>(getActivity().getApplicationContext(),
                  android.R.layout.simple_list_item_1, android.R.id.text1, values);

进入：......（ROOT，SOURCE，DESITNATION）

示例：

ArrayAdapter adapter = ArrayAdapter.createFromResource(getActivity(), R.array.title, android.R.layout.simple_list_item_1);
            lv.setAdapter(adapter);

如果您在Logcat中没有收到任何错误，那么您应该使用断点来查看它何时中断。

Answer 3

感谢Jorge Alfaro，我找到了以下答案：您应该像我一样在每个方法之外创建对象，并在onCreateView内初始化对象。因此，在第一部分中，您将拥有：

DatabaseHandler db;

在onCreateView内：

db = new DatabaseHandler(getActivity());

活动代码到android中的Fragment

3 个答案: