android笔记--在ListView中显示图片及ListView的动态刷新

最近在做一个天气预报的小课题, 其中涉及到了ListView的动态刷新, 以及如何在ListView上显示图片.

1. 在ListView上显示图片.

为了实现这个功能, 首先需要定义一个布局文件, 用于显示ListView的每个Item. 比如list_item.xml:

<?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/list_image"
		android:layout_marginTop="6px" android:layout_marginBottom="6px"
		android:layout_marginLeft="6px" android:layout_marginRight="6px"
		android:layout_width="wrap_content" android:layout_height="wrap_content" />
	<TextView android:id="@+id/list_text"
		android:layout_marginLeft="6px" android:layout_marginRight="6px" android:layout_gravity="center_vertical"
		android:layout_width="fill_parent" android:layout_height="wrap_content" />

</LinearLayout>

public class MyListAdapter extends BaseAdapter {
	private Activity context;
	private List<WeatherInfomation> list;

	public MyListAdapter(Activity context, List<WeatherInfomation> list) {
		this.context = context;
		this.list = list;
	}

	@Override
	public View getView(int position, View convertView, ViewGroup parent) {
		LayoutInflater inflater = context.getLayoutInflater();
		View itemView = inflater.inflate(R.layout.list_item, null);
		WeatherInfomation info = list.get(position);
		TextView textView = (TextView) itemView.findViewById(R.id.list_text);
		ImageView imageView = (ImageView) itemView
				.findViewById(R.id.list_image);
		textView.setText(info.getWeatherText());
		imageView.setImageBitmap(info.getWeatherBitmap());
		return itemView;
	}

	@Override
	public int getCount() {
		return list.size();
	}

	@Override
	public Object getItem(int position) {
		return list.get(position);
	}

	@Override
	public long getItemId(int position) {
		return position;
	}
}

public class WeatherInfomation {
	/**
	 * 代表天气状况的图片
	 */
	private Bitmap weatherBitmap;
	/**
	 * 具体天气的文字说明
	 */
	private String weatherText;

	public WeatherInfomation(Bitmap weatherBitmap, String weatherText) {
		super();
		this.weatherBitmap = weatherBitmap;
		this.weatherText = weatherText;
	}

	public Bitmap getWeatherBitmap() {
		return weatherBitmap;
	}

	public void setWeatherBitmap(Bitmap weatherBitmap) {
		this.weatherBitmap = weatherBitmap;
	}

	public String getWeatherText() {
		return weatherText;
	}

	public void setWeatherText(String weatherText) {
		this.weatherText = weatherText;
	}

}

infomations = new ArrayList<WeatherInfomation>();
		myListAdapter = new MyListAdapter(MainActivity.this, infomations);
		listView.setAdapter(myListAdapter);

2. 很多朋友都知道, 想要动态刷新listview中的内容, 只要调用在数据发生改变之后调用adapter的notifyDataSetChanged()方法就可以了. 这里需要注意的是所谓的"数据发生改变"到底指的是什么, 比如说如下的代码:

infomations = new ArrayList<WeatherInfomation>();
infomations.add(new WeatherInfomation());

而adapter关联的数据并没有发生变化. 后来我的处理代码是:

infomations.clear();
infomations.add(new WeatherInfomation());