Question

我遇到了一个简单的自定义列表问题。我尝试了几个例子，最终得到了同样的错误。我一直得到的错误是

java.lang.NullPointerException：尝试从空数组中读取

适配器类：

public class CustomList  extends ArrayAdapter<String>   {

        Context context;
        int [] images;
        String [] titleArray;
        String [] descriptionArray;

        CustomList(Context context,String[] titles, int [] images, String [] description) {
            super(context,R.layout.single_row,R.id.textView,titles);
            this.context = context;
            this.images = images;
            this.descriptionArray = description;
        }

        @Override
        public View getView(int position, View convertView, ViewGroup parent) {
            LayoutInflater inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            View row =  inflater.inflate(R.layout.single_row,parent, false);

            ImageView img = (ImageView) row.findViewById(R.id.imageView);
            TextView myTxtTitle = (TextView) row.findViewById(R.id.textView);
            TextView myTxtDescription =  (TextView) row.findViewById(R.id.textView2);

            img.setImageResource(images[position]);
            myTxtTitle.setText(titleArray[position]); // where error is happening?
            myTxtDescription.setText(descriptionArray[position]);

            return row;
        }}

活动类：

public class MainActivity extends AppCompatActivity {

    ListView list;
    String [] name;
    String [] sound;
    int [] images = {
            R.drawable.bird,
            R.drawable.cat,
            R.drawable.cow,
            R.drawable.dog,
            R.drawable.frog
    };
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        Resources res = getResources();
        name = res.getStringArray(R.array.title);
        sound = res.getStringArray(R.array.description);

        list = (ListView) findViewById(R.id.list);

        CustomList customAdapter = new CustomList(this, name, images, sound);
        list.setAdapter(customAdapter);
    }
}

Answer 1

你只是忘了分配标题数组......因此数组是空引用....

String [] titleArray;
String [] descriptionArray;

CustomList(Context context,String[] titles, int [] images, String [] description)
    {
    super(context,R.layout.single_row,R.id.textView,titles);
    this.context = context;
    this.images = images;
    this.descriptionArray = description;


     //addd this to init the array
     this.titleArray = titles;
    }

Answer 2

你需要空检查。

ex）if（titleArray！= null）和if（descriptionArray！= null）

当您尝试使用null数据时会发生这种情况。

java.lang.NullPointerException：尝试从空数组中读取

2 个答案: