java - 如何使用 SQL 数据库在 Fragment 上创建适配器 ListView？

Question

我正在尝试使用这种规范调用或查看 ListView：

这是我的代码。这是名为 EducacionFragment 的片段，在这里我想将布局称为“eventos”：

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;
    }
}'

这是我的名为 Elementos_Eventos 的类，我从数据库中获取所有信息，并放入一个列表中：

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();
    }

这是我的名为 Elemento_Eventos 的类，我在其中一一声明了一个元素：

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******************
 }

最后是我的类 Adaptador_Eventos，我将所有这些信息放在 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;
    }
}

当我调用片段 Educacion 时，它会使我的应用程序因消息而崩溃

不幸的是，Unidas Contigo AC 已停止

这是出现的堆栈跟踪：

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

score 1 · Accepted Answer

上面的代码有两个问题。当一个类第一次加载时，它从 elementos() 函数中的 URL 获取数据，这是通过调用 onCreate() 中的 setAdapter 来实现的。

Android 上不允许主/UI 线程上的网络活动。因此，它将 NetworkOnMainThread 作为异常抛出。

其次，您应该使用 asyncTask 连接到 URL，并最好在 onPostExecute() 中创建 listaElements 列表。

score 0 · Accepted Answer

对于 Adaptador_Eventos 类，更改

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

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

至

public static List<Elemento_Eventos> listaElementos ;

public Elementos_Eventos() {
}

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

对于 EducacionFragment 类，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;
    }
}

至

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;
    }
}

试试看，并使用 AsyncTask 来避免 NetworkOnMainThread 异常。

score 0 · Accepted Answer

您需要创建一个列表变量并使用它在 getCount() 函数中返回对象；

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

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

然后在您的 getCount 函数中：

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

java - 如何使用 SQL 数据库在 Fragment 上创建适配器 ListView？

3 回答 3

Related

Reference