使用SQLIte Asset Helper从数据库中获取数据... 我的数据库包含两个表 - （1）android_metadata （2）topiccontent（_id，UNAME，utopicname）
我创建了一个单独的数据库助手类，其代码如下
public class ExternalDbOpenHelper extends SQLiteAssetHelper {
public static String DB_NAME = "cosmcontent.db";
public ExternalDbOpenHelper(Context context) {
super(context, DB_NAME, null, 1);}
public Cursor getUnits()
{
SQLiteDatabase db = getReadableDatabase();
SQLiteQueryBuilder qb = new SQLiteQueryBuilder();
String [] sqlSelect = {"_id","uname","utopicname"};
String sqlTables = "unitcontent";
qb.setTables(sqlTables);
Cursor c = qb.query(db, sqlSelect, null, null, null, null, "utopicname ASC");
c.moveToFirst();
return c;
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {}}
所以这里的数据我想在我的MainAcitvity上的listview中显示..
经过大量的研究后，我实际上没有使用自定义适配器的代码来填充列表视图。 我想在listview的每一行中显示两列数据。 每行的标题将是来自名为“utopicname”的列的数据，其后面的数据将来自“uname”列。 我试图以升序显示列“utpoicname”中的内容。 所以希望内容frin列“uname”应该与“utopicname”排序顺序相关联。 我不想在我的MainActivity上扩展listactivity。 任何帮助将不胜感激。 我的MainActivity的代码如下 -
public class MainActivity extends Activity
{
private Cursor units;
private ExternalDbOpenHelper dbOpen;
ListView lv;
@Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
dbOpen = new ExternalDbOpenHelper(this);
units = dbOpen.getUnits();
ListView lv = (ListView) findViewById(R.id.list);
lv.setAdapter(new SimpleCursorAdapter(this,R.layout.eaach_row,units,
new String[]{ExternalDbOpenHelper.KEY_UTOPICNAME,ExternalDbOpenHelper.KEY_UNAME},
new int[]{R.id.topicname,R.id.unitname},0));
lv.setOnItemClickListener(new OnItemClickListener()
{
@Override
public void onItemClick(AdapterView<?> a, View v,int position, long id)
{
Toast.makeText(getBaseContext(), "Click", Toast.LENGTH_LONG).show();
}
});
}}
登录CAT
07-01 18:34:12.900: W/SQLiteAssetHelper(1017): copying database from assets...
07-01 18:34:12.900: W/SQLiteAssetHelper(1017): database copy complete
07-01 18:34:12.940: I/SQLiteAssetHelper(1017): successfully ope cosmcontent.db
07-01 18:34:13.032: D/AndroidRuntime(1017): Shutting down VM
07-01 18:34:13.032: W/dalvikvm(1017): threadid=1: thread exiting with uncaught exception (group=0xa6224288)
07-01 18:34:13.036: E/AndroidRuntime(1017): FATAL EXCEPTION: main
07-01 18:34:13.036: E/AndroidRuntime(1017): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.tutscosm/com.example.tutscosm.MainActivity}: java.lang.NullPointerException
07-01 18:34:13.036: E/AndroidRuntime(1017):at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2059)
07-01 18:34:13.036: E/AndroidRuntime(1017): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2084)
07-01 18:34:13.036: E/AndroidRuntime(1017): at android.app.ActivityThread.access$600(ActivityThread.java:130)
07-01 18:34:13.036: E/AndroidRuntime(1017): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1195)
07-01 18:34:13.036: E/AndroidRuntime(1017): at android.os.Handler.dispatchMessage(Handler.java:99)
07-01 18:34:13.036: E/AndroidRuntime(1017): at android.os.Looper.loop(Looper.java:137)
07-01 18:34:13.036: E/AndroidRuntime(1017): at android.app.ActivityThread.main(ActivityThread.java:4745)
07-01 18:34:13.036: E/AndroidRuntime(1017): at java.lang.reflect.Method.invokeNative(Native Method)
07-01 18:34:13.036: E/AndroidRuntime(1017): at java.lang.reflect.Method.invoke(Method.java:511)
07-01 18:34:13.036: E/AndroidRuntime(1017): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
07-01 18:34:13.036: E/AndroidRuntime(1017): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
07-01 18:34:13.036: E/AndroidRuntime(1017): at dalvik.system.NativeStart.main(Native Method)
07-01 18:34:13.036: E/AndroidRuntime(1017): Caused by: java.lang.NullPointerException
07-01 18:34:13.036: E/AndroidRuntime(1017): at com.example.tutscosm.MainActivity.onCreate(MainActivity.java:33)
07-01 18:34:13.036: E/AndroidRuntime(1017): at android.app.Activity.performCreate(Activity.java:5008)
07-01 18:34:13.036: E/AndroidRuntime(1017): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1079)
07-01 18:34:13.036: E/AndroidRuntime(1017): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2023)
07-01 18:34:13.036: E/AndroidRuntime(1017): ... 11 more
activity_main.xml中
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
>
<ListView
android:id="@+id/list"
android:layout_width="fill_parent"
android:layout_height="fill_parent">
</ListView>
</LinearLayout>
eaach_row.xml
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="horizontal"
android:padding="10dp" >
<TextView
android:id="@+id/topicname"
android:layout_width="150dp"
android:layout_height="wrap_content"
android:layout_centerVertical="true" />
<TextView
android:id="@+id/unitname"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="@id/topicname"
android:layout_centerVertical="true"
/>
</RelativeLayout>
答案 0 :(得分：1)
使用CursorAdapter怎么样？还有SimpleCursorAdapter？
标准构造函数。
参数 context ListView与此关联的上下文 SimpleListItemFactory正在运行布局
的资源标识符 布局文件，用于定义此列表项的视图。布局文件 应至少包括“to”
中定义的那些命名视图c 数据库游标。如果光标尚不可用，则可以为null。
来自表示要绑定到UI的数据的列名列表。 如果光标尚不可用，则可以为null。
到这些观点 应显示“from”参数中的列。这些应该都是 TextViews。此列表中的前N个视图被赋予了该值的值 from参数中的前N列。如果光标是，则可以为null 还不可用。 flags用于确定行为的标志 适配器，根据CursorAdapter（Context，Cursor，int）。
ListView listView = (ListView) findViewById(...);
listView.setAdapter(new SimpleCursorAdapter(
this, // The context
R.layout.layoutToShow, // The layout of the row to show
dbOpen.getUnits(), // Here the cursor where the data is, i used .getUnits()
// but it can be anything
new String[] { tables to show }, // here the tables to show
new int[] { where to put data? }, // here where to show? the IDs
// of the layout elements where put data.
0
);
查看SimpleCursorAdapter以获取更多信息，或更多通用课程，如果您需要CursorAdapter
答案 1 :(得分：-1)
你应该这样做：
public Class Units{
String utopicname;
public Units(Strign utopicname){
this.utopicname = utopicname;
}
public void setUtopicName(String utopicname){
this.utopicname=utopicname;
}
public String getUtopicName(){
return utopicname;
}
}
//////////////////////////
ArrayList<Units> units;
Cursor c = dbOpen.getUnits();
do{
Units unit = new Units(c.getString(2));
units.add(unit);
}while(c.moveToNext());
ListView listview = (ListView) findViewById(R.id.listView1);
AdapterLists adapterlists = new AdapterLists(this,R.layout.main_layout, units);
listview.setAdapter(adapterlists);
class AdapterLists extends ArrayAdapter {
Activity context = null;
public AdapterLists(Activity context, int layout,ArrayList<Units> units) {
super(context, layout, canales);
this.context = context;
}
public View getView(final int position, View convertView,ViewGroup parent) {
LayoutInflater inflater = context.getLayoutInflater();
View item = inflater.inflate(R.layout.unit_row, null);
TextView ui_unit_utopicname = (TextView)item.findViewById(R.id.txt_row);
String dat_unit_utopicname = units.get(position).getUtopicName();
ui_unit_utopicname.setText(dat_unit_utopicname);
return item;
}
}
您需要使用TextView（txt_row.xml）创建布局（在layout.xml中）