Android 中适配器的作用是什么

适配器在Android开发中扮演着非常重要的角色，它是连接数据和界面的桥梁。Android中的适配器负责将数据源与界面进行绑定，将数据源中的数据展示在界面上。适配器可以将数据逐条加载到列表、网格视图等控件中，并根据数据的变化更新界面。

java
String[] data = {"apple", "banana", "orange"};
ArrayAdapter adapter = new ArrayAdapter<>(this, android.R.layout.simple_list_item_1, data);
ListView listView = findViewById(R.id.listView);
listView.setAdapter(adapter);

java
public class MyAdapter extends BaseAdapter {
    private List data;
    private Context context;
    public MyAdapter(Context context, List data) {
        this.context = context;
        this.data = data;
    }
    @Override
    public int getCount() {
        return data.size();
    }
    @Override
    public Object getItem(int position) {
        return data.get(position);
    }
    @Override
    public long getItemId(int position) {
        return position;
    }
    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        ViewHolder viewHolder;
        if (convertView == null) {
            convertView = LayoutInflater.from(context).inflate(R.layout.list_item, parent, false);
            viewHolder = new ViewHolder();
            viewHolder.textView = convertView.findViewById(R.id.textView);
            convertView.setTag(viewHolder);
        } else {
            viewHolder = (ViewHolder) convertView.getTag();
        }
        viewHolder.textView.setText(data.get(position));
        return convertView;
    }
    static class ViewHolder {
        TextView textView;
    }
}