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>();@Overridepublic 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;}@Overridepublic 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;}@Overridepublic String getType(Uri uri) {return "sutdent";}@Overridepublic Uri insert(Uri uri, ContentValues values) {return null;}@Overridepublic int delete(Uri uri, String selection, String[] selectionArgs) {return 0;}@Overridepublic int update(Uri uri, ContentValues values, String selection,String[] selectionArgs) {return 0;}}

显示:

public class StudentDataActivity extends ListActivity {private Cursor mCursor;@Overrideprotected 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);}}