android实践项目三玩转listview

玩转listview

讲道理 现在是recyleview的时代了，但是listview还是值得学习
让我们来看看listview的继承关系

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

与recycleview一样listview也是需要3个元素
.1 展示界面列表的view
.2适配器用来给view加载数据
.3数据（图片，文字，或者基本组件）
适配器的种类有多种，一般用的有ArrayAdapter,simpleAdapter和SimpleCursorAdapter。

先写一个基本的listview的案例来熟悉依稀listview的用法

public class ListViewTest extends Activity {
    private ListView listview;
    private String[] data = null;
    private ArrayAdapter<String> adapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.listviewtest);
        listview = (ListView) findViewById(R.id.listview);
        data = new String[] { "1", "2", "3", "4", "5", };
        adapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, data);
        listview.setAdapter(adapter);
    }
}

以上代码很简单，完全满足3个元素的基本要求
下面再来看看其他的

然后再写一个自定义适配器布局 就是把listview的子view自定义

如下所示
主布局如下

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context="com.example.demotest.MainActivity" >

    <ListView
        android:id="@+id/listview"
        android:layout_width="match_parent"
        android:layout_height="match_parent" >
    </ListView>

</LinearLayout>

再是listview中的单个项目的布局

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="horizontal"
    tools:context="com.example.demotest.MainActivity" >

    <ImageView
        android:id="@+id/image"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />

    <TextView
        android:id="@+id/textview1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />

</LinearLayout>

listview单个项目的封装类

public class ListviewItem {
    private String name;
    private int imageid;

    public ListviewItem(String name, int imageid) {
        super();
        this.name = name;
        this.imageid = imageid;
    }

    public String getName() {
        return name;
    }

    public int getImageid() {
        return imageid;
    }

}

继承 ArrayAdapter的适配器ItemAdapter的代码如下:

public class ItemAdapter extends ArrayAdapter<ListviewItem> {
    private int resourecId;

    public ItemAdapter(Context context, int textViewResourceId, List<ListviewItem> objects) {
        super(context, textViewResourceId, objects);
        resourecId = textViewResourceId;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        ListviewItem listitem = getItem(position);
        View view;
        ViewHodler viewHolder;
        if (convertView == null) {
            view = LayoutInflater.from(getContext()).inflate(resourecId, null);
            viewHolder = new ViewHodler();
            viewHolder.image = (ImageView) view.findViewById(R.id.image);
        viewHolder.text1 = (TextView) view.findViewById(R.id.textview1);            view.setTag(viewHolder);
        } else {
            view = convertView;
            viewHolder = (ViewHodler) view.getTag();
        }
        viewHolder.image.setImageResource(listitem.getImageid());
        viewHolder.text1.setText(listitem.getName());
        return view;
    }

    class ViewHodler {
        ImageView image;
        TextView text1;
    }
}

上面的代码还是有点不熟悉，强行记下来吧，挖个坑等以后再补

最后写listviewDiy.java
代码如下：

public class ListViewDiy extends Activity {
    private List<ListviewItem> listviewitems = new ArrayList<ListviewItem>();

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.listviewtest);
        initItems();
        ItemAdapter adapter = new ItemAdapter(this, R.layout.listview_items, listviewitems);
        ListView listview = (ListView) findViewById(R.id.listview);
        listview.setAdapter(adapter);
    }

    private void initItems() {
        ListviewItem listviewitem1=new ListviewItem("1",R.drawable.ic_launcher); listviewitems.add(listviewitem1);
        ListviewItem listviewitem2=new ListviewItem("2",R.drawable.ic_launcher); listviewitems.add(listviewitem2);
        ListviewItem listviewitem3=new ListviewItem("3",R.drawable.ic_launcher); listviewitems.add(listviewitem3);
    }
}

也是根据3元素的结构来写的，代码很简单，主要是前面几个要认识透。不懂的闲死记下来吧。之后看懂源码后在 来补充。坑真多~~

最后在来看看listview的子项的监听事件和增删。

监听事件public void onItemClick (AdapterView

    @Override
    public void onCreateContextMenu(ContextMenu menu, View v, ContextMenuInfo menuInfo) {
        super.onCreateContextMenu(menu, v, menuInfo);
        menu.setHeaderTitle("选择操作");
        menu.add(Menu.NONE, Menu.FIRST + 1, 1, "删除");
        menu.add(Menu.NONE, Menu.FIRST + 2, 2, "取消");

    }

    @Override
    public boolean onContextItemSelected(MenuItem item) {
        AdapterContextMenuInfo acmiRef = (AdapterContextMenuInfo) item.getMenuInfo();// 用来获取item信息哎，重要
        int removeIndex = acmiRef.position;
        switch (item.getItemId()) {
        case Menu.FIRST + 1:
            listviewitems.remove(removeIndex);
            adapter.notifyDataSetChanged();// 删除后刷新ListView
            break;
        case Menu.FIRST + 2:
            break;
        default:
            break;

        }

        return false;
    }