MatrixCursor

ContentProvider对外共享数据的时候的query()方法是需要一个cursor的。 

但是当ContentProvider不是从数据库中去的数据，而又需要返回cursor的时候就需要MatrixCursor。 

示例：

class Student {
	String name;
	int num;

	Student(String name, int num) {
		this.name = name;
		this.num = num;
	}
}

public class StudentDataProvider extends ContentProvider {
	public static final Uri CONTENT_URI = Uri
			.parse("content://com.ipmarco.demo.studentdata.provider");

	public static class Columns {
		public static final String ID = "_id";
		public static final String NAME = "name";
		public static final String NUM = "num";
	}

	private static final ArrayList<Student> sData = new ArrayList<Student>();

	@Override
	public boolean onCreate() {
		sData.add(new Student("fire", 1));
		sData.add(new Student("sam", 2));
		sData.add(new Student("tao", 3));
		sData.add(new Student("dian", 4));
		sData.add(new Student("li", 5));
		sData.add(new Student("liu", 6));

		return true;
	}

	@Override
	public Cursor query(Uri uri, String[] projection, String selection,
			String[] selectionArgs, String sortOrder) {
		final MatrixCursor c = new MatrixCursor(new String[] { Columns.ID,
				Columns.NAME, Columns.NUM });
		for (int i = 0; i < sData.size(); ++i) {
			final Student student = sData.get(i);
			c.addRow(new Object[]{Integer.valueOf(i),student.name,Integer.valueOf(student.num)});
		}
		return c;
	}

	@Override
	public String getType(Uri uri) {
		return "sutdent";
	}

	@Override
	public Uri insert(Uri uri, ContentValues values) {
		return null;
	}

	@Override
	public int delete(Uri uri, String selection, String[] selectionArgs) {
		return 0;
	}

	@Override
	public int update(Uri uri, ContentValues values, String selection,
			String[] selectionArgs) {
		return 0;
	}

}

显示:

public class StudentDataActivity extends ListActivity {
	private Cursor mCursor;

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);

		mCursor = getContentResolver().query(StudentDataProvider.CONTENT_URI,
				null, null, null, null);
		SimpleCursorAdapter adapter = new SimpleCursorAdapter(this,
				R.layout.two_line_list_item, mCursor, new String[] {
						StudentDataProvider.Columns.NAME,
						StudentDataProvider.Columns.NUM }, new int[] {
						R.id.text1, R.id.text2 });
		setListAdapter(adapter);
	}
}