我有一个自定义的ListView和一个数据库，我正在尝试从数据库中填充ListView，但始终无法正常工作。
我的代码：
public class MainActivity extends ListFragment {
public sql myDbHelper;
public SQLiteDatabase db = null;
public List<String> mostrar, mostrar2;
AdaptadorTitulares adapter;
public ListView list;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// if extending Activity
View root = inflater.inflate(R.layout.activity_main, container, false);
try {
myDbHelper = new sql(getActivity());
myDbHelper.createDataBase(getActivity());
} catch (Exception e) {
}
new threadbd().execute();
list = (ListView) root.findViewById(android.R.id.list);
list.setOnItemClickListener(new OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> arg0, View arg1, int posicion, long arg3) {
String bebida=mostrar.get(posicion);
String precio=mostrar2.get(posicion);
//Toast.makeText(getApplicationContext(), "El precio es: " + precio + "Y la bebida es: " + bebida, Toast.LENGTH_LONG).show();
}
});
return root;
}// end onCreate
class AdaptadorTitulares extends BaseAdapter {
private Activity mActivityAct;
private LayoutInflater mInflater;
private ArrayList<Titular> mLItems;
public AdaptadorTitulares(Activity a, ArrayList<Titular> it) {
try {
mActivityAct = a;
mLItems = it;
mInflater = (LayoutInflater) mActivityAct
.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
} catch (Exception e) {
}
}
public class VistaH {
public TextView nombree;
public TextView grupoo;
}
@Override
public int getCount() {
return mLItems.size();
}
@Override
public Object getItem(int position) {
return position;
}
@Override
public long getItemId(int position) {
return position;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
View vi = convertView;
VistaH vh = null;
if (vi == null) {
vi = mInflater.inflate(R.layout.target_item, null);
vh = new VistaH();
vh.nombree = (TextView) vi.findViewById(R.id.item_title);
vh.grupoo = (TextView) vi.findViewById(R.id.item_counter);
vi.setTag(vh);
}
vh = (VistaH) vi.getTag();
Titular notice = mLItems.get(position);
vh.nombree.setText(notice.getDate());
vh.grupoo.setText(notice.getTitle());
return vi;
}
@Override
public void unregisterDataSetObserver(DataSetObserver observer) {
if (observer != null) {
super.unregisterDataSetObserver(observer);
}
}
}
private class threadbd extends AsyncTask<Void, Void, Void> {
@Override
protected Void doInBackground(Void... params) {
myDbHelper.openDataBase();
db = myDbHelper.getReadableDatabase();
Cursor c = db.rawQuery("SELECT id FROM lista order by id desc",
null);
c.moveToFirst();
int num = c.getInt(0);
mostrar = new ArrayList<String>(num);
mostrar2 = new ArrayList<String>(num);
for (int i = 0; i <= num; i++) {
Cursor d = db.rawQuery(
"SELECT nombre, precio FROM lista WHERE id=" + i + "",
null);
if (d.moveToFirst()) {
mostrar.add(d.getString(0));
mostrar2.add(String.valueOf(d.getDouble(1)));
}
}// fin for
return null;
}// end InBackground
protected void onPostExecute(Void result) {
Titular titular;
ArrayList<Titular> mList = new ArrayList<Titular>();
for (int i = 0; i < mostrar.size(); i++) {
try {
titular = new Titular(mostrar.get(i), mostrar2.get(i));
mList.add(titular);
} catch (Exception e) {
}
AdaptadorTitulares actualizaAdapter=new AdaptadorTitulares(getActivity(), mList);
list.setAdapter(actualizaAdapter);
}
}
}
}
Titular.java
public class Titular {
private String date;
private String title;
public Titular(String date, String title) {
// Recibe el nombre de la canción, grupo y su tiempo
this.date = date;
this.title = title;
}
public String getDate() {
return date;
}
public void setDate(String date) {
this.date = date;
}
public String getTitle() {
return title;
}
public void setTitle(String title) {
this.title = title;
}
}
sql.java
public class sql extends SQLiteOpenHelper
{
private static String DB_PATH = "/data/data/com.example.listprueba/databases/";
private static String DB_NAME = "prueba";
private final Context myContext;
private SQLiteDatabase myDataBase;
public sql(Context context)
{
super(context, DB_NAME, null, 1);
this.myContext = context;
}
public void createDataBase(Context contexto) throws IOException
{
boolean dbExist = checkDataBase();
if (dbExist)
{
} else
{
this.getReadableDatabase();
try
{
copyDataBase();
} catch (IOException e)
{
throw new Error("Error copiado Base de datos");
}
}
}
private boolean checkDataBase()
{
SQLiteDatabase checkDB = null;
try
{
String myPath = DB_PATH + DB_NAME;
checkDB = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);
} catch (SQLiteException e)
{
}
if (checkDB != null)
{
checkDB.close();
}
return checkDB != null ? true : false;
}
private void copyDataBase() throws IOException
{
InputStream myInput = myContext.getAssets().open(DB_NAME);
String outFileName = DB_PATH + DB_NAME;
OutputStream myOutput = new FileOutputStream(outFileName);
byte[] buffer = new byte[1024];
int length;
while ((length = myInput.read(buffer)) > 0)
{
myOutput.write(buffer, 0, length);
}
// Liberamos los streams
myOutput.flush();
myOutput.close();
myInput.close();
}
public void openDataBase() throws SQLException
{
String myPath = DB_PATH + DB_NAME;
myDataBase = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);
}
public synchronized void close()
{
if (myDataBase != null)
myDataBase.close();
super.close();
}
@Override
public void onCreate(SQLiteDatabase db)
{
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion)
{
}
}
activity_mail.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
<ListView
android:id="@android:id/list"
android:layout_width="wrap_content"
android:layout_height="match_parent" >
</ListView>
</LinearLayout>
target_item.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="48dp"
android:background="#F3F3F3">
<!-- icon -->
<ImageView
android:id="@+id/item_icon"
android:layout_width="32dp"
android:layout_height="32dp"
android:layout_alignParentLeft="true"
android:layout_marginLeft="8dp"
android:layout_marginRight="8dp"
android:layout_marginTop="8dp"
android:src="@drawable/ic_action_help"
/>
<!-- title -->
<TextView
android:id="@+id/item_title"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_toRightOf="@+id/item_icon"
android:layout_alignBaseline="@+id/item_counter"
android:textSize="18dp" />
<!-- counter -->
<TextView
android:id="@+id/item_counter"
android:layout_width="50dp"
android:layout_height="32dp"
android:layout_alignParentRight="true"
android:layout_marginRight="8dp"
android:layout_marginTop="8dp"
android:background="@drawable/rectangle"
android:gravity="center"
android:textColor="#FFFFFF"
android:textSize="12sp"
android:textStyle="bold" />
</RelativeLayout>
错误
06-08 22:35:31.091: E/AndroidRuntime(1470): FATAL EXCEPTION: main
06-08 22:35:31.091: E/AndroidRuntime(1470): Process: com.example.listprueba, PID: 1470
06-08 22:35:31.091: E/AndroidRuntime(1470): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.listprueba/com.example.listprueba.MainActivity}: java.lang.ClassCastException: com.example.listprueba.MainActivity cannot be cast to android.app.Activity
06-08 22:35:31.091: E/AndroidRuntime(1470): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2121)
06-08 22:35:31.091: E/AndroidRuntime(1470): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
06-08 22:35:31.091: E/AndroidRuntime(1470): at android.app.ActivityThread.access$800(ActivityThread.java:135)
06-08 22:35:31.091: E/AndroidRuntime(1470): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
06-08 22:35:31.091: E/AndroidRuntime(1470): at android.os.Handler.dispatchMessage(Handler.java:102)
06-08 22:35:31.091: E/AndroidRuntime(1470): at android.os.Looper.loop(Looper.java:136)
06-08 22:35:31.091: E/AndroidRuntime(1470): at android.app.ActivityThread.main(ActivityThread.java:5017)
06-08 22:35:31.091: E/AndroidRuntime(1470): at java.lang.reflect.Method.invokeNative(Native Method)
06-08 22:35:31.091: E/AndroidRuntime(1470): at java.lang.reflect.Method.invoke(Method.java:515)
06-08 22:35:31.091: E/AndroidRuntime(1470): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
06-08 22:35:31.091: E/AndroidRuntime(1470): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
06-08 22:35:31.091: E/AndroidRuntime(1470): at dalvik.system.NativeStart.main(Native Method)
06-08 22:35:31.091: E/AndroidRuntime(1470): Caused by: java.lang.ClassCastException: com.example.listprueba.MainActivity cannot be cast to android.app.Activity
06-08 22:35:31.091: E/AndroidRuntime(1470): at android.app.Instrumentation.newActivity(Instrumentation.java:1061)
06-08 22:35:31.091: E/AndroidRuntime(1470): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2112)
06-08 22:35:31.091: E/AndroidRuntime(1470): ... 11 more
你知道哪里可以出错吗？我应该改变什么吗？，如果我扩展ListActivity类可以完美地工作。
我不知道如何扩展Fragments而不是ListActivity ....
答案 0 :(得分：0)
尝试让MainActivity扩展FragmentActivity，然后创建一个新的类，ListFragment可以扩展Fragment。现在，您可以在数据库中使用数据填充ListView。在这里查看这个很好的教程＆gt;＆gt; http://www.vogella.com/tutorials/AndroidListView/article.html#listfragments