android– 当Activity启动时不会出现ExpandableListView

概述Yayy,编码非常有趣.这是我创建一个链接到sqllite数据库的ExpandableListView的第三次尝试.最后一个版本在检索数据时工作正常,但在我需要删除或编辑项目时效果不是很好.它基于Api演示,expandableListView1和2.Api代码建议我将我的信息存储在一个数组中,然后才能将它放入Expandable

Yayy,编码非常有趣.这是我创建一个链接到sqllite数据库的ExpandableListVIEw的第三次尝试.最后一个版本在检索数据时工作正常,但在我需要删除或编辑项目时效果不是很好.它基于API演示,expandableListVIEw 1和2.API代码建议我将我的信息存储在一个数组中,然后才能将它放入ExpandableListVIEw.我想我们都可以看到删除和更新存储在数组中的项目的问题.我决定重新开始,用更清洁的东西.

以下代码是我尝试创建一个用sqllite db值填充expandableListVIEw的活动.但是,活动开始时没有任何反应,甚至不是例外.

我假设我的问题在于browseVIEw.setAdapter(mAdapter);但我真的不知道我在说什么,也无法证明这一点！如果我将上面的内容更改为listadapter,则会抛出nullpointerexception.

最后,应该注意我的getChildren游标直接传递了我的groupCursor.这只是因为我还没弄清楚这里发生了什么！ Babysteps.

我在这里走在正确的轨道上吗？谢谢参观.

public class browseActivity extends ExpandableListActivity {final private String[] asColumnsToReturn = {    Items.ITEMS_table_name + "." + Items.ITEMS_ITEM,    Items.ITEMS_table_name + "." + Items.ITEMS_DESC,    Items.ITEMS_table_name + "." + Items.ITEMS_ID };@OverrIDepublic voID onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentVIEw(R.layout.browse);DbHelper dbh = new DbHelper(this.getApplicationContext());sqliteDatabase db = dbh.getWritableDatabase();sqlitequeryBuilder queryBuilder = new sqlitequeryBuilder();queryBuilder.settables(Items.ITEMS_table_name);ExpandableListVIEw browseVIEw = (ExpandableListVIEw)findVIEwByID(androID.R.ID.List);Cursor mCursor = queryBuilder.query(db, asColumnsToReturn, null, null,        null, null, Items.DEFAulT_SORT_ORDER);startManagingCursor(mCursor);SimpleCursorTreeAdapter mAdapter = new SimpleCursorTreeAdapter(this,        mCursor, R.layout.row, R.layout.exprow,        new String[] { Items.ITEMS_ITEM }, new int[] { R.ID.txtItem },        R.layout.exprow, R.layout.exprow, new String[] { Items.ITEMS_DESC },        new int[] { R.ID.dscItem }) {    @OverrIDe    protected Cursor getChildrenCursor(Cursor groupCursor) {        return groupCursor;    }};browseVIEw.setAdapter(mAdapter);}}***START NEW OF NEW CLASS file***public class DbHelper extends sqliteOpenHelper  {private static final int DATABASE_VERSION = 1;private static final String DB_name = "itemList.db";DbHelper(Context context) {super(context, DB_name, null, DATABASE_VERSION);}   @OverrIDepublic voID onCreate(sqliteDatabase db){db.execsql("CREATE table " + Items.ITEMS_table_name + " ("    + BaseColumns._ID + " INTEGER PRIMARY KEY autoINCREMENT ,"    + Items.ITEMS_ITEM + " TEXT," + Items.ITEMS_DESC + " TEXT,"    + Items.ITEMS_MANU + " TEXT," + Items.ITEMS_UPC + " TEXT," +   Items.ITEMS_NWEIGHT + " TEXT," + Items.ITEMS_AWEIGHT + " TEXT)");} @OverrIDepublic voID onUpgrade(sqliteDatabase db, int oldVersion, int newVersion) {}@OverrIDepublic voID onopen(sqliteDatabase db){super.onopen(db);}}***START OF NEW CLASS file***public class ItemDatabase {private ItemDatabase() {}public static final class Items implements BaseColumns {private Items() {}public static final String ITEMS_table_name = "table_itemList";public static final String ITEMS_ID = "_ID";public static final String ITEMS_ITEM = "item";public static final String ITEMS_DESC = "description";public static final String ITEMS_MANU = "manufacturer";public static final String ITEMS_UPC = "upc";public static final String ITEMS_NWEIGHT = "netweight";public static final String ITEMS_AWEIGHT = "actualweight";public static final String DEFAulT_SORT_ORDER = "item ASC";}

并且“浏览”xml文件：

<?xml version="1.0" enCoding="utf-8"?><linearLayoutxmlns:androID="http://schemas.androID.com/apk/res/androID"androID:layout_wIDth="fill_parent"androID:layout_height="fill_parent" androID:orIEntation="vertical"><ExpandableListVIEw androID:ID = "@androID:ID/List" androID:layout_height="fill_parent" androID:layout_wIDth="fill_parent"androID:clickable="true"></ExpandableListVIEw></linearLayout>

解决方法:

这是因为我直接通过getChildrenCursor()方法传递了Group游标.您必须在方法内创建一个新的Cursor.

@OverrIDe    protected Cursor getChildrenCursor(Cursor groupCursor) {        String tempGroup = groupCursor.getString(groupCursor                .getColumnIndex(Items.ITEMS_ITEM));        DbHelper dbh = new DbHelper(browseActivity.this);        sqliteDatabase db = dbh.getWritableDatabase();        String sqlString = "SELECT " + Items.ITEMS_ID + ", "                + Items.ITEMS_DESC + ", " + Items.ITEMS_MANU + ", "                + Items.ITEMS_NWEIGHT + ", " + Items.ITEMS_AWEIGHT + ", "                + Items.ITEMS_UPC + " FROM " + Items.ITEMS_table_name                + " WHERE " + Items.ITEMS_ITEM + "=" + "'" + tempGroup                + "'";        Cursor mCursor = db.rawquery(sqlString, null);        return mCursor;    }

和行布局文件：

<?xml version="1.0" enCoding="utf-8"?><linearLayout xmlns:androID="http://schemas.androID.com/apk/res/androID"androID:ID="@+ID/linearLayout1" androID:layout_wIDth="fill_parent" androID:layout_height="fill_parent"androID:orIEntation="vertical"><TextVIEw androID:layout_gravity="center_vertical|right" androID:ID="@+ID/txtItem" androID:text="Item" androID:layout_height="wrap_content" androID:layout_wIDth="fill_parent" androID:textSize="15dip"></TextVIEw><TextVIEw androID:layout_gravity="center_vertical|right" androID:ID="@+ID/dscItemTwo" androID:text="Desciption" androID:layout_height="wrap_content" androID:layout_wIDth="fill_parent" androID:textStyle="italic"androID:textcolor="#666666"></TextVIEw></linearLayout>

最后是expRow布局(它有点长,我有很多表行.我必须承认事情的名字也很差.我只是想让它工作之前我做得很漂亮！)：

<?xml version="1.0" enCoding="utf-8"?><tableLayout xmlns:androID="http://schemas.androID.com/apk/res/androID"androID:layout_wIDth="fill_parent"androID:layout_height="fill_parent"androID:layout_span = "2"androID:stretchColumns="0"><tableRow androID:layout_height="wrap_content" androID:ID="@+ID/tableRow1" androID:layout_gravity="right" androID:layout_wIDth="wrap_content">    <tableRow     androID:layout_height="wrap_content"     androID:layout_wIDth="fill_parent"    androID:layout_weight = "1"     androID:ID="@+ID/tableRow10"    androID:layout_gravity="right"    >        <TextVIEw         androID:layout_marginRight="1dip"         androID:textcolor="#994020"         androID:layout_height="wrap_content"         androID:layout_gravity="right"         androID:layout_wIDth="wrap_content"         androID:text="Manufacturer"         androID:ID="@+ID/manuItem"        ></TextVIEw>    </tableRow>    <tableRow     androID:layout_height="wrap_content"     androID:ID="@+ID/tableRow11"     androID:layout_wIDth="wrap_content"    ></tableRow>   </tableRow>    <tableRow     androID:layout_height="wrap_content"     androID:layout_wIDth="fill_parent"     androID:ID="@+ID/tableRow2"    >        <tableRow         androID:layout_height="wrap_content"         androID:layout_wIDth="fill_parent"         androID:ID="@+ID/tableRow9"        androID:layout_gravity="right"        androID:layout_weight="1"        >            <TextVIEw             androID:layout_marginRight="1dip"            androID:textcolor="#994020"             androID:layout_height="wrap_content"             androID:layout_gravity="right"             androID:layout_wIDth="wrap_content"             androID:text="Description"             androID:ID="@+ID/dscItem"            ></TextVIEw>        </tableRow>        <tableRow         androID:layout_height="wrap_content"         androID:layout_wIDth="wrap_content"         androID:ID="@+ID/tableRow8"        ></tableRow>     </tableRow>        <tableRow         androID:layout_height="wrap_content"         androID:ID="@+ID/tableRow3"         androID:layout_wIDth="fill_parent"        >            <tableRow             androID:layout_height="wrap_content"             androID:layout_wIDth="wrap_content"             androID:ID="@+ID/tableRow6"             androID:layout_gravity="right"             androID:baselineAligned="true">                <TextVIEw                 androID:layout_marginRight="1dip"                 androID:textcolor="#994020"                  androID:layout_height="wrap_content"                  androID:layout_gravity="right"                  androID:text="Net Weight"                  androID:ID="@+ID/nweightitem"                  androID:layout_wIDth="wrap_content"                  ></TextVIEw>            </tableRow>            <tableRow             androID:layout_height="wrap_content"             androID:layout_wIDth="wrap_content"             androID:ID="@+ID/tableRow7"             >                <TextVIEw                 androID:layout_marginRight="1dip"                androID:layout_gravity="right"                androID:layout_height="wrap_content"                 androID:layout_wIDth="wrap_content"                 androID:text="ounces"                 androID:textStyle="italic"                androID:ID="@+ID/textVIEw1"                 ></TextVIEw>            </tableRow>        </tableRow>        <tableRow         androID:layout_height="wrap_content"          androID:ID="@+ID/tableRow5"          androID:layout_wIDth="wrap_content"         >            <tableRow             androID:layout_height="wrap_content"             androID:layout_wIDth="fill_parent"             androID:ID="@+ID/tableRow12"            androID:layout_weight="1"            androID:layout_gravity="right"            >                <TextVIEw                 androID:layout_marginRight="1dip"                 androID:textcolor="#994020"                 androID:layout_height="wrap_content"                 androID:layout_gravity="right"                 androID:layout_wIDth="wrap_content"                 androID:text="Actual Weight"                 androID:ID="@+ID/aweightitem"                ></TextVIEw>            </tableRow>            <tableRow             androID:layout_height="wrap_content"             androID:layout_wIDth="wrap_content"             androID:ID="@+ID/tableRow13"            >            <TextVIEw                androID:layout_marginRight="1dip"                androID:layout_gravity="right"                androID:layout_height="wrap_content"                 androID:layout_wIDth="wrap_content"                 androID:text="ounces"                 androID:textStyle="italic"                androID:ID="@+ID/textVIEw111"                 ></TextVIEw>            </tableRow>        </tableRow>        <tableRow         androID:ID="@+ID/tableRow4"         androID:layout_wIDth="wrap_content"         androID:layout_height="wrap_content"         >            <tableRow             androID:layout_height="wrap_content"             androID:layout_wIDth="fill_parent"            androID:layout_weight="1"            androID:layout_gravity="right"             androID:ID="@+ID/tableRow14"            >                <TextVIEw                 androID:layout_marginRight="1dip"                 androID:textcolor="#994020"                 androID:layout_height="wrap_content"                 androID:layout_gravity="right"                 androID:layout_wIDth="wrap_content"                 androID:text="UPC"                 androID:ID="@+ID/upcItem"                ></TextVIEw>            </tableRow>            <tableRow             androID:layout_height="wrap_content"             androID:layout_wIDth="wrap_content"             androID:ID="@+ID/tableRow15"            ></tableRow>        </tableRow> </tableLayout>

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