Question

我一直试图将listView填充到一个活动上，但我的listView保持为null，即使在初始化之后也是如此。我检查了错误日志并通过调试器运行它，我得出结论，我没有正确初始化它，虽然我不确定在哪里。

MainActivity

avItem.asset.metadata[titleIndex]

适配器

  public class DisplayCountryActivity extends AppCompatActivity {

    ListView listView;


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

        // Construct the data source
        ArrayList<Country> countries = new ArrayList<>();
        // Create the adapter to convert the array to views

        //context=this;
         listView = (ListView) findViewById(R.id.list_view);

        Cursor cursor = getContentResolver().query(Contract.Country.contentUri, null, null, null, null);

        while(cursor.moveToNext()) {
            countries.add(new Country(cursor.getString(cursor.getColumnIndex("country")),cursor.getDouble(cursor.getColumnIndex("capital")),
                    cursor.getString(cursor.getColumnIndex("area")),cursor.getInt(cursor.getColumnIndex("population")),cursor.getString(cursor.getColumnIndex("official_lang"))));
        }


            CountryAdaptor adapter = new CountryAdaptor(this, countries);

            // Attach the adapter to a ListView
           listView.setAdapter(adapter);

    }


}

列表视图

    public class CountryAdaptor extends ArrayAdapter<Country> {

    private static LayoutInflater inflater = null;
    public CountryAdaptor(Context context, ArrayList<Country> users) {
        super(context, 0, users);
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        // Get the data item for this position
        Country country = getItem(position);
        // Check if an existing view is being reused, otherwise inflate the view
        if (convertView == null) {
            convertView = inflater.inflate(R.layout.country_item, parent, false);
        }
        // Lookup view for data population
        TextView countryTv = (TextView) convertView.findViewById(R.id.dp_country);
        TextView capitalTv = (TextView) convertView.findViewById(R.id.dp_capital);
        TextView areaTv = (TextView) convertView.findViewById(R.id.dp_area);
        TextView populationTv = (TextView) convertView.findViewById(R.id.dp_population);
        TextView officialLanguageTv = (TextView) convertView.findViewById(R.id.dp_official_language);

        // Populate the data into the template view using the data object
        countryTv.setText(country.getCountry());
        capitalTv.setText(country.getCapital());
        areaTv.setText(country.numberToString(country.getArea()));
        populationTv.setText(country.numberToString(country.getArea()));
        officialLanguageTv.setText(country.getOfficial_lang());

        // Return the completed view to render on screen
        return convertView;
    }
}

Answer 1

所以我解决了这个问题。首先，为了清除空气，当我尝试使用我的xml文件初始化时，列表视图变量为null。我的错误是我将listview xml文件作为独立文件，没有格式化。所以基本上我的错误是没有将ListView标签放在我正在使用的内容xml文件中。我所要做的就是将ListView标记添加到我的内容xml文件

我的ListView为空，我不明白为什么

1 个答案: