6.1.5 GridView详解

Android中的数据能够通过GridView类实现表格化展现，它也属于列表类型的控件，其继承关系如下：
java.lang.Object
   ↳ android.view.View
     ↳ android.view.ViewGroup
       ↳ android.widget.AdapterView<T extends android.widget.Adapter>
         ↳ android.widget.AbsListView
           ↳ android.widget.GridView
GridView控件应用案例效果如图6-10所示。
 


图6-10 GridView控件使用效果图
程序代码请参考代码清单6-8：
【代码清单6-8】 chapter6_4/src/com/work/GridView_1.java

public class GridView_1 extends Activity {
	@Override
	public void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);

		setContentView(R.layout.grid);

		GridView g = (GridView) findViewById(R.id.myGrid);
		g.setAdapter(new ImageAdapter(this));

		g.setOnItemSelectedListener(new OnItemSelectedListener() {
			public void onItemSelected(AdapterView<?> parent, View view,
					int position, long id) {
				Toast.makeText(GridView_1.this, "图片ID：" + mThumbIds[position],
						Toast.LENGTH_SHORT).show();
			}

			public void onNothingSelected(AdapterView<?> parent) {
			}
		});
	}

	private Integer[] mThumbIds = { R.drawable.yellowimage,
			R.drawable.redimage, R.drawable.icon, R.drawable.blueimage,
			R.drawable.photo1962, R.drawable.photo189, R.drawable.photo1803,
			R.drawable.photo1796, R.drawable.photo1732, R.drawable.photo1553,
			R.drawable.photo1537, R.drawable.photo1503, R.drawable.photo1453,
			R.drawable.photo1450, R.drawable.photo1447, R.drawable.photo1441,
			R.drawable.photo1433, R.drawable.photo1432, R.drawable.photo1431,
			R.drawable.photo1426, R.drawable.photo1425, R.drawable.photo1424,
			R.drawable.photo1423, R.drawable.photo1422, R.drawable.photo142,
			R.drawable.photo140, R.drawable.photo1220, R.drawable.photo1208,
			R.drawable.photo1207, R.drawable.photo101209, };

	public class ImageAdapter extends BaseAdapter {
		private Context mContext;
		public ImageAdapter(Context c) {
			mContext = c;
		}

		public int getCount() {
			return mThumbIds.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;
			if (convertView == null) {
				imageView = new ImageView(mContext);
				imageView.setLayoutParams(new GridView.LayoutParams(60, 60));
				imageView.setPadding(8, 8, 8, 8);
			} else {
				imageView = (ImageView) convertView;
			}
			imageView.setImageResource(mThumbIds[position]);
			return imageView;
		}
	}
}

代码的关键是实现BaseAdapter适配器类——ImageAdapter，代码如下：

public View getView(int position, View convertView, ViewGroup parent) {
			ImageView imageView;
			if (convertView == null) {
				imageView = new ImageView(mContext);
				imageView.setLayoutParams(new GridView.LayoutParams(60, 60));
				imageView.setPadding(8, 8, 8, 8);
			} else {
				imageView = (ImageView) convertView;
			}
			imageView.setImageResource(mThumbIds[position]);
			return imageView;
		}

在convertView为null的时候实例化控件，imageView.setLayoutParams(new GridView.LayoutParams(60, 60)是设置一个单元格中图片大小是60×60像素。imageView.setPadding(8, 8, 8,设定GridView的单元格与其中的图片之间上、下、左、右空白。
布局文件chapter6_4/res/layout/grid.xml：

<?xml version="1.0" encoding="utf-8"?>
<GridView xmlns:android="http://schemas.android.com/apk/res/android" 
    android:id="@+id/myGrid2"
	android:layout_width="fill_parent" 
	android:layout_height="fill_parent"
    android:verticalSpacing="10dp"    
    android:horizontalSpacing="10dp"
    android:numColumns="auto_fit"
    android:columnWidth="60dp"
    android:gravity="center"
/> 

android:verticalSpacing="10dp"是两行之间的边距，android:horizontalSpacing="10dp"是两列之间的边距。android:numColumns="auto_fit"GridView列数设置为自动，android:columnWidth="60dp"是每列的宽度，也就是项目的宽度。android:gravity="center"是居中。
                                                   出自《Android开发案例驱动教程》第六章