Question

美好的一天，我的自定义适配器没有填充我的listviews有问题。我收到这个错误：

java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ListView.setAdapter(android.widget.ListAdapter)' on a null object reference
                                                                                at com.bestworkouts.sheikoworkout.MyWorkout$1.onChildClick(MyWorkout.java:64)

让我觉得我的arraylist是空的..这就是我称之为适配器的地方：

ArrayList<CustomObject> w29 = new ArrayList<CustomObject>();
    w29.add(new CustomObject("Squat", "65%", "6", "150", false));

    final CustomListViewAdapter customListViewAdapter = new CustomListViewAdapter(this, w29);


    expandableListView = (ExpandableListView) findViewById(R.id.listViewWorkouts);
    Workouts_details = DataProvider.getInfo();
    Workout_list = new ArrayList<>(Workouts_details.keySet());
    mAdapter = new WorkoutsAdapter(this, Workouts_details, Workout_list);

    final ListView listViewFri = (ListView) findViewById(R.id.listViewFri);
    final ListView listViewMon = (ListView) findViewById(R.id.listViewMon);
    final ListView listViewWed = (ListView) findViewById(R.id.listViewWed);

    expandableListView.setAdapter(mAdapter);

    expandableListView.setOnChildClickListener(new ExpandableListView.OnChildClickListener() {
        @Override
        public boolean onChildClick(ExpandableListView parent, View v, int groupPosition, int childPosition, long id) {
            if (groupPosition == 0) {
                if (childPosition == 0) {
                    listViewMon.setAdapter(customListViewAdapter);
                    listViewFri.setAdapter(customListViewAdapter);
                    listViewWed.setAdapter(customListViewAdapter);
                    Intent intent = new Intent(getApplicationContext(), WorkoutDaysActivity.class);
                    startActivity(intent);

这是适配器：

public class CustomListViewAdapter extends BaseAdapter {

private LayoutInflater inflater;
public ArrayList<CustomObject> objects;
boolean[] checkBoxState;
CustomObject data[] = null;




private class ViewHolder {
    TextView txtExercise;
    TextView txtPercent;
    TextView txtReps;
    TextView txtWeight;
    CheckBox check1;
}

public void addAdapterItem(CustomObject item) {
    objects.add(item);
}

public CustomListViewAdapter(Context context, ArrayList<CustomObject> objects) {
    inflater = LayoutInflater.from(context);
    this.objects = objects;
    checkBoxState= new boolean[objects.size()];
}

public int getCount() {
    return objects.size();
}

public CustomObject getItem(int position) {
    return objects.get(position);
}

public long getItemId(int position) {
    return position;
}

public View getView(final int position, View convertView, ViewGroup parent) {
    ViewHolder holder = null;
    if(convertView == null) {
        holder = new ViewHolder();
        convertView = inflater.inflate(R.layout.workout_item, null);
        holder.txtExercise = (TextView) convertView.findViewById(R.id.txtExercise);
        holder.txtPercent = (TextView) convertView.findViewById(R.id.txtPercentage);
        holder.txtReps = (TextView) convertView.findViewById(R.id.txtReps);
        holder.txtWeight = (TextView) convertView.findViewById(R.id.txtWeight);
        holder.check1 = (CheckBox) convertView.findViewById(R.id.check1);
        convertView.setTag(holder);
    } else {
        holder = (ViewHolder) convertView.getTag();
    }
    holder.txtExercise.setText(objects.get(position).getExercise());
    holder.txtPercent.setText(objects.get(position).getPercent());
    holder.txtReps.setText(objects.get(position).getReps());
    holder.txtWeight.setText(objects.get(position).getWeight());
    holder.check1.setChecked(checkBoxState[position]);

    holder.check1.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            if(((CheckBox)v).isChecked()) {
                checkBoxState[position] = true;
            } else {
                checkBoxState[position] = false;
            }
        }
    });


    return convertView;
}
}

这是customobject类：

public class CustomObject {

private String exercise;
private String percent;
private String reps;
private String weight;
private boolean check1;

public CustomObject(String exercise, String percent, String reps, String weight, boolean check1) {
    this.exercise = exercise;
    this.percent = percent;
    this.reps = reps;
    this.weight = weight;
    this.check1 = check1;
}

public String getExercise() {
    return exercise;
}

public String getPercent() {
    return percent;
}

public String getReps() {
    return reps;
}

public String getWeight() {
    return weight;
}

//    public CheckBox getCheck1() {
//        return check1;
//    }
}

这是WorkoutDaysActivity（发送意图的地方）的一部分（我已经包含了on create方法以及设置的3个标签。

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


    mToolBar = activateToolbarWithHomeEnabled();
    setUpNavigationDrawer();
//        setSupportActionBar(toolbar);
//        getSupportActionBar().setDisplayHomeAsUpEnabled(true);
    // Create the adapter that will return a fragment for each of the three
    // primary sections of the activity.
    mSectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager());

    // Set up the ViewPager with the sections adapter.
    mViewPager = (ViewPager) findViewById(R.id.container);
    mViewPager.setAdapter(mSectionsPagerAdapter);

    TabLayout tabLayout = (TabLayout) findViewById(R.id.tabs);
    tabLayout.setupWithViewPager(mViewPager);


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


        switch (getArguments().getInt(ARG_SECTION_NUMBER)) {
            case 1:
                View rootView = inflater.inflate(R.layout.fragment_workout_days, container, false);
//                    CustomListViewAdapter mCustomListViewAdapter;
//                    mCustomListViewAdapter = new CustomListViewAdapter(this, )
//                    ListView listViewMon = (ListView) rootView.findViewById(R.id.listViewMon);
//                    listViewMon.setAdapter(mCustomListViewAdapter);


                return rootView;
            case 2: View rootView2 = inflater.inflate(R.layout.fragment_sub_page1, container, false);
                TextView textView2 = (TextView) rootView2.findViewById(R.id.textView2);
                textView2.setText("Workout 29 Week 1");
                return rootView2;
            case 3:
                View rootView3 = inflater.inflate(R.layout.fragment_sub_page2, container, false);
                TextView textView3 = (TextView) rootView3.findViewById(R.id.txtFrag3);
                textView3.setText(getString(R.string.section_format, getArguments().getInt(ARG_SECTION_NUMBER)));
                return rootView3;
            default: View rootView4 = inflater.inflate(R.layout.fragment_workout_days, container, false);
                TextView textView4 = (TextView) rootView4.findViewById(R.id.txtFrag1);
                textView4.setText(getString(R.string.section_format, getArguments().getInt(ARG_SECTION_NUMBER)));
                return rootView4;
        }
//
    }
}

感谢您的帮助！

Answer 1

错误很明显，listView对象之一为null：

final ListView listViewFri = (ListView) findViewById(R.id.listViewFri);
final ListView listViewMon = (ListView) findViewById(R.id.listViewMon);
final ListView listViewWed = (ListView) findViewById(R.id.listViewWed);

检查视图ID是否正确

Answer 2

它表示列表视图为空，您可以检查您的xml以确保正确添加列表视图。您是否还可以将活动代码粘贴到“创建”或“xml膨胀”或setContentView。您没有正确设置视图。你的arraylists很好，你的适配器代码似乎也很好看

Answer 3

错误很简单。在获取listView的引用时，您在编写ID时遇到了一些错误。例如R.id.list（列表是这里的ID）

也许您正在使用您在布局的.xml中找不到的其他参考资料。

ListView没有填充数据

3 个答案: