如何使用 SQL 數據庫在 Fragment 上創建 Adapter ListView？

Question

我正在嘗試調用或查看具有此類規范的 ListView：

線框

這是我的代碼。 這是名為 EducacionFragment 的片段，這里是我想將布局稱為“eventos”的地方：

public class EducacionFragment extends ListFragment{
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {

        View view = inflater.inflate(R.layout.eventos_layout, container, false);

        //((MainActivity) getActivity()).getSupportActionBar().setTitle("Eventos");
        //Elementos_Eventos elementos_eventos = new Elementos_Eventos();

        ListView listview =(ListView)view.findViewById(R.id.listView2);

        Adaptador_Eventos adaptador = new Adaptador_Eventos(getActivity());

        //adaptador = new Adaptador_Eventos(getActivity());

        listview.setAdapter(adaptador);

        return view;
    }
}'

這是我的名為 Elementos_Eventos 的類，我從我的數據庫中獲取所有信息，並放入一個列表中：

public class Elementos_Eventos {

    //URL to get JSON Array
    private static String url = "http://ucwm.co.nf/Evento_app.php";

    //JSON Node Names
    private static final String TAG_EVENTOS = "eventos";
    private static final String TAG_ID = "idEvento";
    private static final String TAG_NAME = "Nombre";
    private static final String TAG_DESCRIP = "Descripcion";
    private static final String TAG_FECHAI = "FechaInicio";
    private static final String TAG_HORA = "Hora";
    private static final String TAG_FECHAF = "FechaFinal";
    private static final String TAG_LUGAR = "Lugar";
    private static JSONArray eventos = null;

    public static List<Elemento_Eventos> listaElementos = elementos();

    public Elementos_Eventos() {
        listaElementos = elementos();
    }

    static Elemento_Eventos elemento(int id) {
        return listaElementos.get(id);
    }

    public static ArrayList<Elemento_Eventos> elementos() {

        JSONParser jParser = new JSONParser();
        JSONObject json;

        // Getting JSON from URL
        json = jParser.getJSONFromUrl(url);

        ArrayList<Elemento_Eventos> elementos;
        elementos = null;
        try {
            // Getting JSON Array from URL
            eventos = json.getJSONArray(TAG_EVENTOS);

            elementos = new ArrayList<Elemento_Eventos>();

            for (int i = 0; i < eventos.length(); i++) {

                JSONObject c = eventos.getJSONObject(i);

                // Storing  JSON item in a Variable
                String id = c.getString(TAG_ID);
                String nombre = c.getString(TAG_NAME);
                String descripcion = c.getString(TAG_DESCRIP);
                String fechaInicio = c.getString(TAG_FECHAI);
                String hora = c.getString(TAG_HORA);
                String fechaFinal = c.getString(TAG_FECHAF);
                String lugar = c.getString(TAG_LUGAR);

                elementos.add(new Elemento_Eventos(id, nombre,descripcion, fechaInicio, hora, fechaFinal, lugar));
            }

        }
        catch (JSONException e) {
            e.printStackTrace();
        }
        return elementos;
    }

    public List<String> listaElementos()
    {
        ArrayList<String> todos = new ArrayList<String>();
        for (Elemento_Eventos e:listaElementos)
            todos.add(e.getNombre());
        return todos;
    }

    public static int size() {
        return listaElementos.size();
    }

這是我的名為Elemento_Eventos的類，我在其中一一聲明了一個元素：

public class Elemento_Eventos {
    private String id;
    private String nombre;
    private String descripcion;
    private String feInicio;
    private String hora;
    private String feFinal;
    private String lugar;

    public Elemento_Eventos(String id,String nombre, String descripcion, String feInicio, String hora, String feFinal, String lugar){
        setId(id);
        setNombre(nombre);
        setDescripcion(descripcion);
        setFeInicio(feInicio);
        setHora(hora);
        setFeFinal(feFinal);
        setLugar(lugar);
    }

    //*********INICIO DE LOS SETS******************
    public void setId(String id){
        this.id=id;
    }

    public void setNombre(String nombre){
        this.nombre=nombre;
    }

    public void setDescripcion(String descripcion){
        this.descripcion=descripcion;
    }

    public void setFeInicio(String feInicio){
        this.feInicio=feInicio;
    }

    public void setHora(String hora){
        this.hora=hora;
    }

    public void setFeFinal(String feFinal){
        this.feFinal=feFinal;
    }

    public void setLugar(String lugar){
        this.lugar=lugar;
    }

    //*********FINAL DE LOS SETS******************

    //*********INICIO DE LOS GETS******************
    public String getId(){
        return id;
    }

    public String getNombre(){
        return nombre;
    }

    public String getDescripcion(){
        return descripcion;
    }

    public String getFeInicio(){
        return feInicio;
    }

    public String getHora(){
        return hora;
    }

    public String getFeFinal(){
        return feFinal;
    }

    public String getLugar(){
        return lugar;
    }
    //*********FINAL DE LOS SETS******************
 }

最后是我的名為 Adaptador_Eventos 的類，我將所有這些信息放在 textViews 中：

public class Adaptador_Eventos extends BaseAdapter{

    private final Activity actividad;

    public Adaptador_Eventos(Activity actividad) {
        super();
        this.actividad = actividad;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        Elemento_Eventos elemento = Elementos_Eventos.elemento(position);

        LayoutInflater inflater = actividad.getLayoutInflater();
        View view = inflater.inflate(R.layout.elemento_eventos, null,true);
        TextView nombreDelEvento, lugar, fecha, descripcion;
        ImageView logo_tipo;
        nombreDelEvento = (TextView) view.findViewById(R.id.nom_evento);
        lugar = (TextView) view.findViewById(R.id.lugar_evento);
        fecha = (TextView) view.findViewById(R.id.fecha_evento);
        descripcion = (TextView) view.findViewById(R.id.desc_evento);
        logo_tipo = (ImageView) view.findViewById(R.id.imageView);

        nombreDelEvento.setText(elemento.getNombre());
        lugar.setText(elemento.getLugar());
        fecha.setText(elemento.getFeInicio());
        descripcion.setText(elemento.getDescripcion());

        int id = R.drawable.kcc;
        logo_tipo.setImageResource(id);
        logo_tipo.setScaleType(ImageView.ScaleType.FIT_END);
        return view;
    }

    @Override
    public int getCount() {
        return Elementos_Eventos.size();
    }

    @Override
    public Object getItem(int position) {
        return Elementos_Eventos.elemento(position);
    }

    @Override
    public long getItemId(int position) {
        return position;
    }
}

當我調用片段 Educacion 時，它會用消息使我的應用程序崩潰

不幸的是，Unidas Contigo AC 已停止

這是出現的堆棧跟蹤：

 11-12 05:10:00.279 7414-7414/? D/dalvikvm? Late-enabling CheckJNI 11-12 05:10:01.059 7414-7414/com.example.juanisaac.unidascontigoac W/dalvikvm? VFY: unable to find class referenced in signature (Landroid/view/SearchEvent;) 11-12 05:10:01.095 7414-7414/com.example.juanisaac.unidascontigoac I/dalvikvm? Could not find method android.view.Window$Callback.onSearchRequested, referenced from method android.support.v7.internal.view.WindowCallbackWrapper.onSearchRequested 11-12 05:10:01.107 7414-7414/com.example.juanisaac.unidascontigoac W/dalvikvm? VFY: unable to resolve interface method 15449: Landroid/view/Window$Callback;.onSearchRequested (Landroid/view/SearchEvent;)Z 11-12 05:10:01.119 7414-7414/com.example.juanisaac.unidascontigoac D/dalvikvm? VFY: replacing opcode 0x72 at 0x0002 11-12 05:10:01.123 7414-7414/com.example.juanisaac.unidascontigoac I/dalvikvm? Could not find method android.view.Window$Callback.onWindowStartingActionMode, referenced from method android.support.v7.internal.view.WindowCallbackWrapper.onWindowStartingActionMode 11-12 05:10:01.139 7414-7414/com.example.juanisaac.unidascontigoac W/dalvikvm? VFY: unable to resolve interface method 15453: Landroid/view/Window$Callback;.onWindowStartingActionMode (Landroid/view/ActionMode$Callback;I)Landroid/view/ActionMode; 11-12 05:10:01.139 7414-7414/com.example.juanisaac.unidascontigoac D/dalvikvm? VFY: replacing opcode 0x72 at 0x0002 11-12 05:10:01.407 7414-7414/com.example.juanisaac.unidascontigoac I/AppCompatViewInflater? app:theme is now deprecated. Please move to using android:theme instead. 11-12 05:10:01.419 7414-7414/com.example.juanisaac.unidascontigoac I/dalvikvm? Could not find method android.content.res.TypedArray.getChangingConfigurations, referenced from method android.support.v7.internal.widget.TintTypedArray.getChangingConfigurations 11-12 05:10:01.423 7414-7414/com.example.juanisaac.unidascontigoac W/dalvikvm? VFY: unable to resolve virtual method 426: Landroid/content/res/TypedArray;.getChangingConfigurations ()I 11-12 05:10:01.423 7414-7414/com.example.juanisaac.unidascontigoac D/dalvikvm? VFY: replacing opcode 0x6e at 0x0002 11-12 05:10:01.431 7414-7414/com.example.juanisaac.unidascontigoac I/dalvikvm? Could not find method android.content.res.TypedArray.getType, referenced from method android.support.v7.internal.widget.TintTypedArray.getType 11-12 05:10:01.439 7414-7414/com.example.juanisaac.unidascontigoac W/dalvikvm? VFY: unable to resolve virtual method 448: Landroid/content/res/TypedArray;.getType (I)I 11-12 05:10:01.439 7414-7414/com.example.juanisaac.unidascontigoac D/dalvikvm? VFY: replacing opcode 0x6e at 0x0002 11-12 05:10:01.479 7414-7414/com.example.juanisaac.unidascontigoac I/AppCompatViewInflater? app:theme is now deprecated. Please move to using android:theme instead. 11-12 05:10:01.547 7414-7416/com.example.juanisaac.unidascontigoac D/dalvikvm? GC_CONCURRENT freed 192K, 3% free 8841K/9068K, paused 13ms+0ms, total 26ms 11-12 05:10:01.631 7414-7414/com.example.juanisaac.unidascontigoac D/dalvikvm? GC_FOR_ALLOC freed 5K, 3% free 8858K/9068K, paused 13ms, total 14ms 11-12 05:10:01.707 7414-7414/com.example.juanisaac.unidascontigoac I/dalvikvm-heap? Grow heap (frag case) to 10.120MB for 1517220-byte allocation 11-12 05:10:01.719 7414-7424/com.example.juanisaac.unidascontigoac D/dalvikvm? GC_FOR_ALLOC freed <1K, 3% free 10340K/10552K, paused 14ms, total 14ms 11-12 05:10:01.739 7414-7416/com.example.juanisaac.unidascontigoac D/dalvikvm? GC_CONCURRENT freed 0K, 3% free 10340K/10552K, paused 8ms+0ms, total 11ms 11-12 05:10:01.759 7414-7414/com.example.juanisaac.unidascontigoac D/dalvikvm? GC_FOR_ALLOC freed <1K, 3% free 10339K/10552K, paused 6ms, total 6ms 11-12 05:10:01.875 7414-7414/com.example.juanisaac.unidascontigoac I/dalvikvm-heap? Grow heap (frag case) to 15.908MB for 6068844-byte allocation 11-12 05:10:01.887 7414-7424/com.example.juanisaac.unidascontigoac D/dalvikvm? GC_FOR_ALLOC freed <1K, 2% free 16266K/16480K, paused 12ms, total 12ms 11-12 05:10:01.919 7414-7416/com.example.juanisaac.unidascontigoac D/dalvikvm? GC_CONCURRENT freed <1K, 2% free 16266K/16480K, paused 7ms+0ms, total 20ms 11-12 05:10:02.051 7414-7414/com.example.juanisaac.unidascontigoac D/libEGL? loaded /system/lib/egl/libEGL_genymotion.so 11-12 05:10:02.067 7414-7414/com.example.juanisaac.unidascontigoac D/? HostConnection::get() New Host Connection established 0xb92c56a8, tid 7414 11-12 05:10:02.087 7414-7414/com.example.juanisaac.unidascontigoac D/libEGL? loaded /system/lib/egl/libGLESv1_CM_genymotion.so 11-12 05:10:02.087 7414-7414/com.example.juanisaac.unidascontigoac D/libEGL? loaded /system/lib/egl/libGLESv2_genymotion.so 11-12 05:10:02.147 7414-7414/com.example.juanisaac.unidascontigoac W/EGL_genymotion? eglSurfaceAttrib not implemented 11-12 05:10:02.171 7414-7414/com.example.juanisaac.unidascontigoac D/OpenGLRenderer? Enabling debug mode 0 11-12 05:10:04.511 7414-7414/com.example.juanisaac.unidascontigoac I/Choreographer? Skipped 46 frames! The application may be doing too much work on its main thread. 11-12 05:10:05.599 7414-7414/com.example.juanisaac.unidascontigoac W/dalvikvm? Exception Landroid/os/NetworkOnMainThreadException; thrown while initializing Lcom/example/juanisaac/unidascontigoac/Elementos_Eventos; 11-12 05:10:05.599 7414-7414/com.example.juanisaac.unidascontigoac D/AndroidRuntime? Shutting down VM 11-12 05:10:05.603 7414-7414/com.example.juanisaac.unidascontigoac W/dalvikvm? threadid=1: thread exiting with uncaught exception (group=0xa620e908) 11-12 05:10:05.615 7414-7414/com.example.juanisaac.unidascontigoac E/AndroidRuntime? FATAL EXCEPTION: main java.lang.ExceptionInInitializerError at com.example.juanisaac.unidascontigoac.Adaptador_Eventos.getCount(Adaptador_Eventos.java:57) at android.widget.ListView.setAdapter(ListView.java:462) at com.example.juanisaac.unidascontigoac.Fragments.EducacionFragment.onCreateView(EducacionFragment.java:40) at android.support.v4.app.Fragment.performCreateView(Fragment.java:1962) at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1016) at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1197) at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:738) at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1562) at android.support.v4.app.FragmentManagerImpl$1.run(FragmentManager.java:483) at android.os.Handler.handleCallback(Handler.java:725) at android.os.Handler.dispatchMessage(Handler.java:92) at android.os.Looper.loop(Looper.java:137) at android.app.ActivityThread.main(ActivityThread.java:5041) at java.lang.reflect.Method.invokeNative(Native Method) at java.lang.reflect.Method.invoke(Method.java:511) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560) at dalvik.system.NativeStart.main(Native Method) Caused by: android.os.NetworkOnMainThreadException at android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1117) at java.net.InetAddress.lookupHostByName(InetAddress.java:385) at java.net.InetAddress.getAllByNameImpl(InetAddress.java:236) at java.net.InetAddress.getAllByName(InetAddress.java:214) at org.apache.http.impl.conn.DefaultClientConnectionOperator.openConnection(DefaultClientConnectionOperator.java:137) at org.apache.http.impl.conn.AbstractPoolEntry.open(AbstractPoolEntry.java:164) at org.apache.http.impl.conn.AbstractPooledConnAdapter.open(AbstractPooledConnAdapter.java:119) at org.apache.http.impl.client.DefaultRequestDirector.execute(DefaultRequestDirector.java:360) at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:555) at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:487) at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:465) at com.example.juanisaac.unidascontigoac.JSONParser.getJSONFromUrl(JSONParser.java:37) at com.example.juanisaac.unidascontigoac.Elementos_Eventos.elementos(Elementos_Eventos.java:55) at com.example.juanisaac.unidascontigoac.Elementos_Eventos.<clinit>(Elementos_Eventos.java:39) at com.example.juanisaac.unidascontigoac.Adaptador_Eventos.getCount(Adaptador_Eventos.java:57) at android.widget.ListView.setAdapter(ListView.java:462) at com.example.juanisaac.unidascontigoac.Fragments.EducacionFragment.onCreateView(EducacionFragment.java:40) at android.support.v4.app.Fragment.performCreateView(Fragment.java:1962) at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1016) at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1197) at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:738) at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1562) at android.support.v4.app.FragmentManagerImpl$1.run(FragmentManager.java:483) at android.os.Handler.handleCallback(Handler.java:725) at android.os.Handler.dispatchMessage(Handler.java:92) at android.os.Looper.loop(Looper.java:137) at android.app.ActivityThread.main(ActivityThread.java:5041) at java.lang.reflect.Method.invokeNative(Native Method) at java.lang.reflect.Method.invoke(Method.java:511) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560) at dalvik.system.NativeStart.main(Native Method) 11-12 05:10:08.059 7414-7414/com.example.juanisaac.unidascontigoac I/Process? Sending signal. PID: 7414 SIG: 9

Answer 1

上面的代碼有兩個問題。 當一個類第一次加載時，它從 elementos() 函數中的 URL 獲取數據，這是通過調用 onCreate() 中的 setAdapter 發生的。

Android 上不允許主/UI 線程上的網絡活動。 因此，它拋出 NetworkOnMainThread 作為異常。

其次，您應該使用 asyncTask 連接到 URL，並最好在 onPostExecute() 中創建 listaElements 列表。

Answer 2

您需要創建一個列表變量並使用它來返回 getCount() 函數中的對象；

List<Elemento_Eventos> myList = new ArrayList<Elemento_Eventos>();

public Adaptador_Eventos(Activity actividad,  List<Elemento_Eventos> myList){
    super();
    this.actividad = actividad;
    this.myList = myList;
}

然后在你的 getCount 函數中：

@Override
public int getCount() {
    return myList.size();
}

Answer 3

對於類 Adaptador_Eventos，更改

public static List<Elemento_Eventos> listaElementos = elementos();

public Elementos_Eventos() {
    listaElementos = elementos();
}

到

public static List<Elemento_Eventos> listaElementos ;

public Elementos_Eventos() {
}

public static void init(){
    listaElementos = elementos();
}

對於類 EducacionFragment，更改

public class EducacionFragment extends ListFragment{
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {

        View view = inflater.inflate(R.layout.eventos_layout, container, false);

        //((MainActivity) getActivity()).getSupportActionBar().setTitle("Eventos");
        //Elementos_Eventos elementos_eventos = new Elementos_Eventos();

        ListView listview =(ListView)view.findViewById(R.id.listView2);

        Adaptador_Eventos adaptador = new Adaptador_Eventos(getActivity());

        //adaptador = new Adaptador_Eventos(getActivity());

        listview.setAdapter(adaptador);

        return view;
    }
}

到

public class EducacionFragment extends ListFragment{
    private ListView listview;
    private Adaptador_Eventos adaptador;
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {

        View view = inflater.inflate(R.layout.eventos_layout, container, false);

        //((MainActivity) getActivity()).getSupportActionBar().setTitle("Eventos");
        //Elementos_Eventos elementos_eventos = new Elementos_Eventos();

        listview =(ListView)view.findViewById(R.id.listView2);

        adaptador = new Adaptador_Eventos(getActivity());

        //adaptador = new Adaptador_Eventos(getActivity());

        new AsyncTask(){
            @Override
            protected Object doInBackground(Object[] params) {
                Elementos_Eventos.init();
                return null;
            }

            @Override
            protected void onPostExecute(Object o) {
                super.onPostExecute(o);
                listview.setAdapter(adaptador);
            }
        }.execute();

        return view;
    }
}

試試看，並使用 AsyncTask 來避免 NetworkOnMainThread 異常。