android 开发技巧(16)--充分利用ListView的头视图

实现一个这样的功能：在界面上提供一个现实图片的相册和一个显示数字的列表，当向下滚动界面时，相册随着移动，直到图片消失

实现思路：如果把Gallery和ListView两个控件置于ScrollView中，会出现一些问题，因为ListView本身就是ScrollView
比较简单的思路就是：ListView提供了头视图(Header View)与尾视图(Footer View)，把Gallery设置为ListView的头视图

ImageAdapter.java

public class ImageAdapter extends BaseAdapter {
  private Context mContext;

  private Integer[] mImageIds = { R.drawable.sample_0,
      R.drawable.sample_1, R.drawable.sample_2, R.drawable.sample_3,
      R.drawable.sample_4, R.drawable.sample_5, R.drawable.sample_6,
      R.drawable.sample_7 };

  public ImageAdapter(Context c) {
    mContext = c;
  }

  public int getCount() {
    return mImageIds.length;
  }

  public Object getItem(int position) {
    return position;
  }

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

  public View getView(int position, View convertView, ViewGroup parent) {
    ImageView imageView = new ImageView(mContext);

    imageView.setImageResource(mImageIds[position]);
    imageView.setLayoutParams(new Gallery.LayoutParams(500, 500));
    imageView.setScaleType(ImageView.ScaleType.FIT_XY);

    return imageView;
  }
}

主布局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" android:orientation="vertical" >

    <ListView  android:id="@+id/main_listview" android:layout_width="fill_parent" android:layout_height="wrap_content" />

</LinearLayout>

头部布局header2.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" android:orientation="vertical" >

    <Gallery  android:id="@+id/listview_header_gallery" android:layout_width="fill_parent" android:layout_height="wrap_content" />

</LinearLayout>

列表项布局list_item2.xml

<?xml version="1.0" encoding="utf-8"?>
<TextView xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="fill_parent" android:layout_height="fill_parent" android:padding="15dp" android:textSize="40sp" />

主程序：

public class Hack28Activity extends Activity {

    private static final String[] NUMBERS = { "1", "2", "3", "4", "5",
            "6", "7", "8" };
    private Gallery mGallery;
    private View mHeader;
    private ListView mListView;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_hack28);
        mListView = (ListView) findViewById(R.id.main_listview);

        LayoutInflater inflator = LayoutInflater.from(this);//创建需要被填充的XML文件
        mHeader = inflator.inflate(R.layout.header2, mListView, false);
        mGallery = (Gallery) mHeader
                .findViewById(R.id.listview_header_gallery);
        mGallery.setAdapter(new ImageAdapter(this));
        //替换头视图原始的LayoutParams为ListView设置适配器
        ListView.LayoutParams params = new ListView.LayoutParams(
                ListView.LayoutParams.FILL_PARENT,
                ListView.LayoutParams.WRAP_CONTENT);
        mHeader.setLayoutParams(params);
        mListView.addHeaderView(mHeader, null, false);//将头视图添加到ListView中

        ArrayAdapter<String> adapter = new ArrayAdapter<String>(this,
                R.layout.list_item2, NUMBERS);
        mListView.setAdapter(adapter);

        mListView.setOnItemClickListener(new AdapterView.OnItemClickListener() {

            @Override
            public void onItemClick(AdapterView<?> parent, View view,
                                    int position, long id) {
                mGallery.setSelection(position - 1, true);
            }
        });
    }
}