如何使用 ArrayAdapter<myClass>

Question

ArrayList<MyClass> myList = new ArrayList<MyClass>();

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

ArrayAdapter<MyClass> adapter = new ArrayAdapter<MyClass>(this, R.layout.row,
    to, myList.);
listView.setAdapter(adapter);

班级：我的班级

class MyClass {
    public String reason;
    public long long_val;
}

我在布局中创建了 row.xml，但不知道如何使用 ArrayAdapter 在 ListView 中同时显示原因和 long_val。

Answer 1

为您的类实现自定义适配器：

public class MyClassAdapter extends ArrayAdapter<MyClass> {

    private static class ViewHolder {
        private TextView itemView;
    }

    public MyClassAdapter(Context context, int textViewResourceId, ArrayList<MyClass> items) {
        super(context, textViewResourceId, items);
    }

    public View getView(int position, View convertView, ViewGroup parent) {

        if (convertView == null) {
            convertView = LayoutInflater.from(this.getContext())
            .inflate(R.layout.listview_association, parent, false);

            viewHolder = new ViewHolder();
            viewHolder.itemView = (TextView) convertView.findViewById(R.id.ItemView);

            convertView.setTag(viewHolder);
        } else {
            viewHolder = (ViewHolder) convertView.getTag();
        }

        MyClass item = getItem(position);
        if (item!= null) {
            // My layout has only one TextView
                // do whatever you want with your string and long
            viewHolder.itemView.setText(String.format("%s %d", item.reason, item.long_val));
        }

        return convertView;
    }
}

对于那些不太熟悉 Android 框架的人，这里有更详细的解释：https://github.com/codepath/android_guides/wiki/Using-an-ArrayAdapter-with-ListView。

Answer 2

您可以根据http://developer.android.com/reference/android/widget/ArrayAdapter.html 将toString() 方法添加到MyClass：

无论如何引用 TextView，它都会被数组中每个对象的 toString() 填充。您可以添加自定义对象的列表或数组。覆盖对象的 toString() 方法以确定列表中的项目将显示哪些文本。

class MyClass {

 @Override
 public String toString() {
  return "Hello, world.";
 }
}

Answer 3

我认为这是最好的方法。使用泛型 ArrayAdapter 类并扩展您自己的 Object 适配器，如下所示：

public abstract class GenericArrayAdapter<T> extends ArrayAdapter<T> {

  // Vars
  private LayoutInflater mInflater;

  public GenericArrayAdapter(Context context, ArrayList<T> objects) {
    super(context, 0, objects);
    init(context);
  }

  // Headers
  public abstract void drawText(TextView textView, T object);

  private void init(Context context) {
    this.mInflater = LayoutInflater.from(context);
  }

  @Override public View getView(int position, View convertView, ViewGroup parent) {
    final ViewHolder vh;
    if (convertView == null) {
      convertView = mInflater.inflate(android.R.layout.simple_list_item_1, parent, false);
      vh = new ViewHolder(convertView);
      convertView.setTag(vh);
    } else {
      vh = (ViewHolder) convertView.getTag();
    }

    drawText(vh.textView, getItem(position));

    return convertView;
  }

  static class ViewHolder {

    TextView textView;

    private ViewHolder(View rootView) {
      textView = (TextView) rootView.findViewById(android.R.id.text1);
    }
  }
}

这里是你的适配器（示例）：

public class SizeArrayAdapter extends GenericArrayAdapter<Size> {

  public SizeArrayAdapter(Context context, ArrayList<Size> objects) {
    super(context, objects);
  }

  @Override public void drawText(TextView textView, Size object) {
    textView.setText(object.getName());
  }

}

最后，如何初始化它：

ArrayList<Size> sizes = getArguments().getParcelableArrayList(Constants.ARG_PRODUCT_SIZES);
SizeArrayAdapter sizeArrayAdapter = new SizeArrayAdapter(getActivity(), sizes);
listView.setAdapter(sizeArrayAdapter);

我创建了一个带有 TextView 布局重力可定制 ArrayAdapter 的 Gist：

https://gist.github.com/m3n0R/8822803

Answer 4

子类化 ArrayAdapter 并覆盖方法 getView() 以返回包含您要显示的内容的您自己的视图。

Answer 5

如果您不想为扩展母类而烦恼，这里有一个快速而肮脏的示例，说明如何使用 ArrayAdapter：

class MyClass extends Activity {
    private ArrayAdapter<String> mAdapter = null;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        mAdapter = new ArrayAdapter<String>(getApplicationContext(),
            android.R.layout.simple_dropdown_item_1line, android.R.id.text1);

        final ListView list = (ListView) findViewById(R.id.list);
        list.setAdapter(mAdapter);

        //Add Some Items in your list:
        for (int i = 1; i <= 10; i++) {
            mAdapter.add("Item " + i);
        }

        // And if you want selection feedback:
        list.setOnItemClickListener(new OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                //Do whatever you want with the selected item
                Log.d(TAG, mAdapter.getItem(position) + " has been selected!");
            }
        });
    }
}