百戰(zhàn)經(jīng)典第四戰(zhàn)-玩轉(zhuǎn)ListView

Android用的最多的，也最難用的應(yīng)該就是ListView了，ListView的繼承結(jié)構(gòu)如下：

java.lang.Object
   ?    android.view.View
       ?    android.view.ViewGroup
           ?    android.widget.AdapterView<T extends android.widget.Adapter>
               ?    android.widget.AbsListView
                   ?    android.widget.ListView

listview 三元素：

列表的顯示需要三個元素：

1. ListVeiw 用來展示列表的View。
2. 適配器 用來把數(shù)據(jù)映射到ListView上的中介。
3. 數(shù)據(jù) 具體的將被映射的字符串，圖片，或者基本組件。

根據(jù)列表的適配器類型，列表分為三種，ArrayAdapter，SimpleAdapter和SimpleCursorAdapter

其中以ArrayAdapter最為簡單，只能展示一行字。SimpleAdapter有最好的擴(kuò)充性，可以自定義出各種效果。SimpleCursorAdapter可以認(rèn)為是SimpleAdapter對數(shù)據(jù)庫的簡單結(jié)合，可以方面的把數(shù)據(jù)庫的內(nèi)容以列表的形式展示出來。

一、最簡單的ListView

首先簡單介紹一下ListView的最簡單用法，不用列表項布局文件：

package org.yayun.demo;  
//省略導(dǎo)入包
public class MainActivity extends Activity {  
    private String[] arrays = { "Sunday", "Monday", "Tuesday", "Wednesday",  
            "Thursday", "Friday", "Saturday" };  
    private ListView listView;  
    @Override  
    protected void onCreate(Bundle savedInstanceState) {  
        super.onCreate(savedInstanceState);  
        listView = new ListView(this);  
        listView.setAdapter(new ArrayAdapter<String>(this,  
                android.R.layout.simple_expandable_list_item_1, arrays));//利用ArrayAdapter對數(shù)據(jù)進(jìn)行包裝  
        super.setContentView(listView);//將ListView設(shè)置為顯示界面  
    }  
}

這里使用了ArrayAdapter實(shí)現(xiàn)，直接將arrays中的數(shù)據(jù)引入ListView，滿足簡單的應(yīng)用需求。

實(shí)例運(yùn)行如下：

二、結(jié)合ArrayAdapter實(shí)現(xiàn)較復(fù)雜的ListView

1.main.xml代碼：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical" >
    <ListView
        android:id="@+id/list_view"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content" />
</LinearLayout>

2.fruit_item.xml代碼：（ListView中的單項目）

<?xml version="1.0" encoding="utf-8"?>  
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"  
    android:layout_width="fill_parent"  
    android:layout_height="fill_parent">  
    <ImageView  
        android:id="@+id/fruit_image"  
        android:layout_width="wrap_content"  
        android:layout_height="wrap_content" />  
    <TextView  
        android:id="@+id/fruit_name"  
        android:layout_width="wrap_content"  
        android:layout_height="wrap_content"  
        android:layout_gravity="center"  
        android:layout_marginLeft="10sp" />  
</LinearLayout> 

3.Fruit.java代碼如下：（封裝屬性）

package org.yayun.demo;  

public class Fruit {  
    private String name;  
    private int imageId;  
    public Fruit(String name, int imageId) {  
        this.name = name;  
        this.imageId = imageId;  
    }  
    public String getName() {  
        return name;  
    }  
    public int getImageId() {  
        return imageId;  
    }  
} 

4.集成ArrayAdapter的FruitAdapter.java代碼如下：（適配器類）

package org.yayun.demo;  
//省略導(dǎo)入包
public class FruitAdapter extends ArrayAdapter<Fruit> {  
    private int resourceId;  
    public FruitAdapter(Context context, int textViewResourceId,  
            List<Fruit> objects) {  
        super(context, textViewResourceId, objects);  
        resourceId = textViewResourceId;  
    }  
    @Override  
    public View getView(int position, View convertView, ViewGroup parent) {  
        Fruit fruit = getItem(position);  
        View view;  
        ViewHolder viewHolder;  
        if (convertView == null) {  
            view = LayoutInflater.from(getContext()).inflate(resourceId, null);  
            viewHolder = new ViewHolder();  
            viewHolder.fruitImage = (ImageView) view  
                    .findViewById(R.id.fruit_image);  
            viewHolder.fruitName = (TextView) view  
                    .findViewById(R.id.fruit_name);  
            view.setTag(viewHolder);  
        } else {  
            view = convertView;  
            viewHolder = (ViewHolder) view.getTag();  
        }  
        viewHolder.fruitImage.setImageResource(fruit.getImageId());  
        viewHolder.fruitName.setText(fruit.getName());  
        return view;  
    }  
    class ViewHolder {  
        ImageView fruitImage;  
        TextView fruitName;  
    }  
}  

對代碼不熟悉的同學(xué)不要緊張，這些都是較為固定的寫法，寫多了就可以理解其中的含義了。

5.MainActivity.java代碼如下：

package org.yayun.demo;  
//省略導(dǎo)入包
public class Hello extends Activity {  
    private List<Fruit> fruitList = new ArrayList<Fruit>();  

    public void onCreate(Bundle savedInstanceState) {  
        super.onCreate(savedInstanceState); // 生命周期方法  
        super.setContentView(R.layout.main); // 設(shè)置要使用的布局管理器  
        initFruits();  
        FruitAdapter adapter = new FruitAdapter(Hello.this,  
                R.layout.fruit_item, fruitList);  //適配器
        ListView listView = (ListView) findViewById(R.id.list_view);  
        listView.setAdapter(adapter);  //設(shè)置適配器
    }  

    private void initFruits() {  //數(shù)據(jù)初始化
        Fruit appleFruit = new Fruit("Apple", R.drawable.apple_pic);  
        fruitList.add(appleFruit);  
        Fruit bananaFruit = new Fruit("Banana", R.drawable.banana_pic);  
        fruitList.add(bananaFruit);  
        Fruit orangeFruit = new Fruit("Orange", R.drawable.orange_pic);  
        fruitList.add(orangeFruit);  
        Fruit waterFruit = new Fruit("Apple", R.drawable.watermelon_pic);  
        fruitList.add(waterFruit);  
    }  
}  

運(yùn)行上面的實(shí)例，使得ListView不僅可以顯示文字，也可以顯示圖片，進(jìn)行組合顯示。

三、結(jié)合上下文菜單實(shí)現(xiàn)單項的刪除

修改MainActivity.java程序如下：

package org.yayun.demo;  
//省略導(dǎo)入包
public class Hello extends Activity {  
    private List<Fruit> fruitList = new ArrayList<Fruit>();  
    FruitAdapter adapter;  
    public void onCreate(Bundle savedInstanceState) {  
        super.onCreate(savedInstanceState); // 生命周期方法  
        super.setContentView(R.layout.main); // 設(shè)置要使用的布局管理器  
        initFruits();  
        adapter = new FruitAdapter(Hello.this, R.layout.fruit_item, fruitList);  
        ListView listView = (ListView) findViewById(R.id.list_view);  
        listView.setAdapter(adapter);  
        super.registerForContextMenu(listView);//注冊上下文菜單  
    }  
    @Override  
    public void onCreateContextMenu(ContextMenu menu, View v,// 創(chuàng)建菜單項  
            ContextMenuInfo menuInfo) {  
        super.onCreateContextMenu(menu, v, menuInfo);  
        menu.setHeaderTitle("選擇操作");  
        menu.add(Menu.NONE, Menu.FIRST + 1, 1, "刪除");  
        menu.add(Menu.NONE, Menu.FIRST + 2, 2, "取消");  
    }  
    @Override  
    public boolean onContextItemSelected(MenuItem item) {// 選擇監(jiān)聽  
        AdapterContextMenuInfo acmiRef = (AdapterContextMenuInfo) item  
                .getMenuInfo();// 用來獲取item信息哎，重要  
        int removeIndex = acmiRef.position;  
        switch (item.getItemId()) {  
        case Menu.FIRST + 1:  
            fruitList.remove(removeIndex);  
            adapter.notifyDataSetChanged();// 刪除后刷新ListView  
              break;  
        case Menu.FIRST + 2:  
            break;  
        default:  
            break;  
        }  
        return false;  
    }  
    private void initFruits() {  //初始化數(shù)據(jù)
        Fruit appleFruit = new Fruit("Apple", R.drawable.apple_pic);  
        fruitList.add(appleFruit);  
        Fruit bananaFruit = new Fruit("Banana", R.drawable.banana_pic);  
        fruitList.add(bananaFruit);  
        Fruit orangeFruit = new Fruit("Orange", R.drawable.orange_pic);  
        fruitList.add(orangeFruit);  
        Fruit waterFruit = new Fruit("Apple", R.drawable.watermelon_pic);  
        fruitList.add(waterFruit);  
    }  
} 

運(yùn)行實(shí)例如下：

點(diǎn)擊刪除按鈕后：

總結(jié)

1. super.registerForContextMenu(listView);//注冊上下文菜單
2. adapter.notifyDataSetChanged();// 刪除后刷新ListView
3. AdapterContextMenuInfo acmiRef = (AdapterContextMenuInfo) item.getMenuInfo();// 用來獲取當(dāng)前item信息，重要 int removeIndex = acmiRef.position;//獲取點(diǎn)擊位置的坐標(biāo)