Android Api Demos登顶之路（108）View-->ExpanableLists-->Cursor

最新推荐文章于 2021-05-29 11:09:38 发布

原创最新推荐文章于 2021-05-29 11:09:38 发布 · 496 阅读

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#apidemo #views #expandable #cursor #expandablelistview

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本文介绍了一种使用Cursor为Android中的ExpandableListView设置数据适配器的方法。通过AsyncQueryHandler异步查询联系人及其电话号码数据，并通过CursorTreeAdapter将这些数据展示出来。这种方式适用于从数据库中获取大量分组数据并展示的情况。

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/*本例演示了为ExpandableListView设置数据适配器的第二种方式：Cursor
 */
public class MainActivity extends ExpandableListActivity {
    private static final String[] CONTACTS_PROJECTION = new String[] {
            Contacts._ID, Contacts.DISPLAY_NAME };
    private static final int GROUP_ID_COLUM_INDEX = 0;

    private static final String[] PHONE_NUMBER_PROJECTION = new String[] {
            Phone._ID, Phone.NUMBER };

    // group的标志
    private static final int TOKEN_GROUP = 0;
    // child的标志
    private static final int TOKEN_CHILD = 1;

    // 异步查询类
    private class QueryHandler extends AsyncQueryHandler {
        private CursorTreeAdapter mAdapter;

        // 对未实现的构造函数进行改造，但super的参数是不能变的
        public QueryHandler(Context context, CursorTreeAdapter adapter) {
            super(context.getContentResolver());
            this.mAdapter = adapter;
        }

        // 重写该方法，根据标志位为Adapter设置Cursor
        @Override
        protected void onQueryComplete(int token, Object cookie, Cursor cursor) {
            switch (token) {
            case TOKEN_GROUP:
                mAdapter.setGroupCursor(cursor);
                break;
            case TOKEN_CHILD:
                int groupPosition = (Integer) cookie;
                mAdapter.setChildrenCursor(groupPosition, cursor);
                break;
            }
        }

    }

    private QueryHandler mHandler;
    private CursorTreeAdapter mAdapter;

    private class MyExpandableListAdapter extends SimpleCursorTreeAdapter {

        // 注意这里在构造方法中不需要Cursor cursor参数，避免在主线程中对数据库进行查询
        public MyExpandableListAdapter(Context context, int groupLayout,
                String[] groupFrom, int[] groupTo, int childLayout,
                String[] childFrom, int[] childTo) {
            super(context, null, groupLayout, groupFrom, groupTo, childLayout,
                    childFrom, childTo);
            // TODO Auto-generated constructor stub
        }

        @Override
        protected Cursor getChildrenCursor(Cursor groupCursor) {
            // 构建一个新的Uri的builder，该builder继承此Uri的属性
            Uri.Builder builder = Contacts.CONTENT_URI.buildUpon();
            ContentUris.appendId(builder,
                    groupCursor.getLong(GROUP_ID_COLUM_INDEX));
            // 添加子项的Uri路径
            builder.appendEncodedPath(Contacts.Data.CONTENT_DIRECTORY);
            Uri phoneNumberUri = builder.build();

            // 查询子项数据,由handler负责查询，所次需要返回cursor结果集
            mHandler.startQuery(TOKEN_CHILD, groupCursor.getPosition(),
                    phoneNumberUri, PHONE_NUMBER_PROJECTION, Phone.MIMETYPE
                            + "=?", new String[] { Phone.CONTENT_ITEM_TYPE },
                    null);
            return null;
        }

    }

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

        mAdapter = new MyExpandableListAdapter(
                this,
                // 该布局中只有一个textView
                android.R.layout.simple_expandable_list_item_1,
                new String[] { Contacts.DISPLAY_NAME },
                new int[] { android.R.id.text1 },
                android.R.layout.simple_expandable_list_item_1,
                new String[] { Phone.NUMBER }, new int[] { android.R.id.text1 });
        setListAdapter(mAdapter);
        mHandler = new QueryHandler(this, mAdapter);

        // 查询父项
        mHandler.startQuery(TOKEN_GROUP, null, Contacts.CONTENT_URI,
                CONTACTS_PROJECTION, Contacts.HAS_PHONE_NUMBER+"=1", null, null);
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        mAdapter.changeCursor(null);
        mAdapter=null;
    }
}