xamarin android——資料繫結到控制項（四）

標籤：des   android   c   style   class   blog   

本文為通過自訂欄表適配器定義ListView，以上文為基礎，基於ListActivity。

定義清單項目布局，包含一個圖片顯示，標題和描述

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    android:layout_width="fill_parent"    android:layout_height="80dip">    <ImageView        android:id="@+id/image"        android:layout_width="wrap_content"        android:layout_height="wrap_content" />    <LinearLayout        android:orientation="vertical"        android:layout_width="wrap_content"        android:layout_height="fill_parent"        android:layout_marginLeft="10dip"        android:layout_marginRight="10dip">        <TextView            android:id="@+id/title"            android:layout_width="wrap_content"            android:layout_height="wrap_content" />        <TextView            android:id="@+id/description"            android:layout_width="wrap_content"            android:layout_height="wrap_content" />    </LinearLayout></LinearLayout>

為了使視圖顯示資料，必須自訂配接器。ListView每一個清單項目顯示的是自訂的Model資料，選擇繼承BaseAdapter<T>，T為自訂Model

model類內容

public class Model    {        public string Name {            get;            set;        }        public string Description {            get;            set;        }        public int Image {            get;            set;        }    }

適配器類需要實現兩個方法和兩個屬性：

Count屬性、T類型的this 屬性、GetItemId方法、GetView方法。

this屬性返回指定索引對應的對象資料。

自訂ModelListAdapter代碼：

class ModelListAdapter :BaseAdapter<Model>    {        public List<Model> Models {            get;            set;        }        public ModelListAdapter(List<Model> models)        {            Models = models;        }        #region implemented abstract members of BaseAdapter        public override long GetItemId (int position)        {            return position;        }        public override View GetView (int position, View convertView, ViewGroup parent)        {
　　　　　　  //從資料來源中擷取當前位置對應的對象            var item = Models [position];　　　　　　  //避免重複建立和銷毀清單項目視圖            if (convertView==null) {                LayoutInflater inflater = Application.Context.GetSystemService ("layout_inflater") as LayoutInflater;                convertView = inflater.Inflate (Resource.Layout.CustomItem,null);            }            var image = convertView.FindViewById<ImageView> (Resource.Id.image);            var title = convertView.FindViewById<TextView> (Resource.Id.title);            var description = convertView.FindViewById<TextView> (Resource.Id.description);            image.SetImageResource (item.Image);            title.Text = item.Name;            description.Text = item.Description;            return convertView;        }        public override int Count {            get {                return Models.Count;            }        }        #endregion        #region implemented abstract members of BaseAdapter        public override Model this [int index] {            get {                return Models [index];            }        }        #endregion    }

最後一步，將LiatActivity的ListAdapter賦值為我們自訂的適配器

var models = new List<Model>{                new Model(){ Name="Name",Description="Description",Image = Resource.Drawable.Icon},                new Model(){ Name="Name",Description="Description",Image = Resource.Drawable.Icon},                new Model(){ Name="Name",Description="Description",Image = Resource.Drawable.Icon},                new Model(){ Name="Name",Description="Description",Image = Resource.Drawable.Icon},                new Model(){ Name="Name",Description="Description",Image = Resource.Drawable.Icon},                new Model(){ Name="Name",Description="Description",Image = Resource.Drawable.Icon}            };            this.ListAdapter = new ModelListAdapter (models);

自訂配接器，我們可以進行更靈活的處理。在GetView方法中執行更多的操作，如果只是進行簡單的自訂欄表樣式，可以通過SimpleAdapter快速完成操作。

IList<IDictionary<string,object>> items = new JavaList<IDictionary<string,object>> ();            var item1 = new JavaDictionary<string,object> ();            item1.Add ("name","show name");            item1.Add("description","description");            item1.Add ("image",Resource.Drawable.Icon);            var item2 = new JavaDictionary<string,object> ();            item2.Add ("name","show name");            item2.Add("description","description");            item2.Add ("image",Resource.Drawable.Icon);            items.Add (item1);            items.Add (item2);            this.ListAdapter = new SimpleAdapter (this,items,Resource.Layout.CustomItem,                new string[]{"name","description","image"},new int[]{Resource.Id.title,Resource.Id.description,Resource.Id.image});

items為定義的資料來源k，定義SimpleAdapter傳入參數即可。其中string[] 中定義的值必須等於Dictionary中key的值，string[] 和int[] 兩個參數表示from string[] to int[]。即每個string[]中的值作為key，取得Dictionary中的值，賦值給int[] 中id所對應的視圖。