如何在Android ArrayAdapter中使用对象数组？

Question

我需要使用ArrayAdapter在我的Android应用程序中填充ListView.它说,为了使用ArrayAdapter

例如,如果要在ListView中显示要显示的字符串数组,请使用构造函数初始化新的ArrayAdapter,以指定每个字符串和字符串数组的布局:

ArrayAdapter adapter = new ArrayAdapter(this,android.R.layout.simple_list_item_1,myStringArray);

这个构造函数的参数是:

• 你的应用上下文
• 包含数组中每个字符串的TextView的布局
• 字符串数组

然后只需在ListView上调用setAdapter():

ListView listView =(ListView)findViewById(R.id.listview); listView.setAdapter(适配器);

但是,我没有字符串数组,我有一个包含字符串值的对象数组.

public class Headers {
    private String from;
    private String to;
    private String subject;

    public Headers (String from, String to, String subject){
        this.from = from;
        this.to = to;
        this.subject = subject;
    }

    public String getFrom() { return from; }
    public void setFrom(String from) { this.from = from; }

    public String getTo() { return to; }
    public void setTo(String to) { this.to = to; }

    public String getSubject() { return subject; }
    public void setSubject(String subject) { this.subject = subject; }
}

我的布局确实包含与我的对象中的值对应的TextView.

这是我的ListView布局:

<LinearLayout android:orientation="vertical">
    <ListView android:id="@+id/listOfHeaders" >
</LinearLayout>

以下是ListAdapter填充的ListView中每行的布局:

<LinearLayout android:orientation="horizontal">
    <TextView android:id="@+id/toTextView" />
    <TextView android:id="@+id/fromTextView" />
    <TextView android:id="@+id/subjectTextView" />
</LinearLayout>

Answer 1

使用ArrayAdapter是不够的,您需要扩展ArrayAdapter并创建自定义适配器,这样您就可以覆盖行创建以使用列表布局.请检查此示例:

public class CustomAdapter extends ArrayAdapter<Headers> {

    Context context;
    int layoutResourceId;
    ArrayList<Headers> data = null;

    public CustomAdapter(Context context, int resource, List<Headers> objects) {
        super(context, resource, objects);
        this.layoutResourceId = resource;
        this.context = context;
        this.data = (ArrayList) objects;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        View row = convertView;
        HeaderHolder holder = null;

        if(row == null)
        {
            LayoutInflater inflater = ((Activity)context).getLayoutInflater();
            row = inflater.inflate(layoutResourceId, parent, false);

            holder = new HeaderHolder();
            holder.from = (TextView) row.findViewById(R.id.fromTextView);
            holder.to = (TextView)row.findViewById(R.id.toTextView);
            holder.subject = (TextView)row.findViewById(R.id.subjectTextView);

            row.setTag(holder);
        }
        else
        {
            holder = (HeaderHolder) row.getTag();
        }

        Headers item = data.get(position);
        holder.from.setText(item.getFrom());
        holder.to.setText(item.getTo());
        holder.subject.setText(item.getSubject());

        return row;
    }

    private class HeaderHolder {
        public TextView from;
        public TextView to;
        public TextView subject;

    }
}

对于Activity,在onCreate方法上:

ListView list = (ListView) findViewById(R.id.listView);
ArrayList<Headers> data = new ArrayList<Headers>();
data.add(new Headers("from", "to", "subject"));

ArrayAdapter adapter = new CustomAdapter(this, R.layout.list, data);
list.setAdapter(adapter); 

您可以看到CustomAdapter正在使用HeaderHolder作为ViewHolder模式的一部分,因此列表管理是高效的.