Java ANDROID-使用片段上的数据库填充自定义ListView

我有一个自定义的ListView和一个数据库，我试图从数据库填充该ListView，但总是不起作用

我的代码：

java

activity_mail.xml

你知道哪里会出错吗？如果我扩展了ListActivity类，那么我是否应该更改什么呢

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我不知道如何扩展片段而不是ListActivity…

尝试让MainActivity扩展FragmentActivity，然后创建一个新类，ListFragment可以在其中扩展片段。现在，您可以使用数据库中的数据填充ListView。在这里查看这个不错的教程>>

你应该让你的MainActivity从fragmentActivity扩展，然后创建一个从ListFragment扩展的片段，然后在里面使用这个片段MainActivity@k3v1n4ud3我会试着再说一遍，谢谢。

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);

            }
        }
    }
}

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;
    }
}

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)
    {

    }
}

<?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>

<?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>

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