学习Android之SimpleAdapter显示网络图片

效果图：

此程序基本的知识点是：SimpleAdapter本身是不支持网络图片的， 假设在Map.put（a。b）中 b为一个Bitmap。程序不会报红色字体，而是在控制台输出绿色的字体，例如以下

05-10 15:46:45.474: I/System.out(846): resolveUri failed on bad bitmap uri: android.graphics.Bitmap@43e40c08

要想实现显示网络图片事实上非常easy。使用SimpleAdapter中的方法simpleAdapter.setViewBinder（）。

simpleAdapter.setViewBinder(new ViewBinder() {

			@Override
			public boolean setViewValue(View view, Object data,
					String textRepresentation) {
				if (view instanceof ImageView && data instanceof Bitmap) {
					ImageView iv = (ImageView) view;
					iv.setImageBitmap((Bitmap) data);
					return true;
				}
				return false;
			}
		});

new SimpleAdapter(MainActivity.this,getData(), R.layout.t, new String[] { "images" },new int[] { R.id.ImageVIew_main });

有三个參数view,data,textRepresentation，说说前两个參数，view 是你自己定义布局（如上 R.layout.t）中全部的组件，程序会遍历一边布局中的组件，data是你传的

list<map< , >>（如上getData()方法，返回一个list<map< , >>），程序会遍历每一项数据。接下来用if（）语句筛选就能够了。

既然是网络图片，那就须要权限

 <uses-permission android:name="android.permission.INTERNET" />

代码例如以下：

MainActivity.java

public class MainActivity extends ActionBarActivity {


	ListView listView;
	List<Map<String, ?
>> data;

	String str[] = { "",       //自己加入图片网址 h  t  t  p ://
			"",
			"",
			"" };

	@Override
	public void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		listView = (ListView) findViewById(R.id.LV_main);

		SimpleAdapter simpleAdapter = new SimpleAdapter(MainActivity.this,
				getData(), R.layout.t, new String[] { "images" },
				new int[] { R.id.ImageVIew_main });
		simpleAdapter.setViewBinder(new ViewBinder() {

			@Override
			public boolean setViewValue(View view, Object data,
					String textRepresentation) {
				if (view instanceof ImageView && data instanceof Bitmap) {
					ImageView iv = (ImageView) view;
					iv.setImageBitmap((Bitmap) data);
					return true;
				}
				return false;
			}
		});

		listView.setAdapter(simpleAdapter);
	}

	public List<Map<String, ?>> getData() {
		data = new ArrayList<Map<String, ?
>>();
		for (int i = 0; i < str.length; i++) {
			Map<String, Object> map = new HashMap<String, Object>();

			map.put("images", returnBitMap(str[i]));
			data.add(map);
		}
		return data;

	}

	public Bitmap returnBitMap(String url) {
		URL myFileUrl = null;
		Bitmap bitmap = null;
		try {
			myFileUrl = new URL(url);
		} catch (MalformedURLException e) {
			e.printStackTrace();
		}
		try {
			HttpURLConnection conn = (HttpURLConnection) myFileUrl
					.openConnection();
			conn.setDoInput(true);
			conn.connect();
			InputStream is = conn.getInputStream();
			bitmap = BitmapFactory.decodeStream(is);
			is.close();
		} catch (IOException e) {
			e.printStackTrace();
		}
		return bitmap;
	}
}

activity_main.xml

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

自己定义布局文件

t.xml

<?
xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >
    
    <ImageView 
        android:id="@+id/ImageVIew_main"
        android:layout_width="80dp"
        android:layout_height="80dp"/>

</LinearLayout>