java - 一行有 3 个值的 ListView

Question

我有这个问题:我应该创建一个地址簿，并且名字、姓氏和电话号码必须显示在每一行上。我能够获取这 3 个值，但是当添加它们时，单击按钮后每个值都会插入一行，如何连续显示所有 3 个值？

感谢您提前回复

public class MainActivity extends AppCompatActivity {
    ArrayAdapter<String> adapter;
    EditText nomeV, cognomeV, numeroV;
    ArrayList<String> itemList;
    public ListView listView;
    CustomAdapter customAdapter;

    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        String[] items={"Apple gg","Banana gio ","Clementine add"};





        customAdapter = new CustomAdapter(this, R.layout.list_item, new ArrayList<Persona>());

        listView.setAdapter(customAdapter);



        nomeV = (EditText) findViewById(R.id.nome);
        cognomeV = (EditText) findViewById(R.id.cognome);
        numeroV= (EditText)findViewById(R.id.numero);
        Button btAdd=(Button)findViewById(R.id.btAdd);
        btAdd.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String nomevalue=nomeV.getText().toString();
                String cognomevalue=cognomeV.getText().toString();
                String numerovalue=numeroV.getText().toString();

                // add new item to arraylist

                Persona c = new Persona(
                        nomevalue,
                        cognomevalue,
                        numerovalue);
                customAdapter.add(c);

                // notify listview of data changed
                adapter.notifyDataSetChanged();
            }

        });





    }

}

class Persona {
    String nome;
    String cognome;
    String numero;

    public Persona(String nome, String cognome, String numero) {
        this.nome=nome;
        this.cognome=cognome;
        this.numero=numero;


    }

    public String getNome() {
        return nome;
    }

    public String getCognome() {
        return cognome;
    }

    public String getNumero() {
        return numero;
    }

}

public class CustomAdapter extends ArrayAdapter<Persona> {
    private int resource;
    private LayoutInflater inflater;

    public CustomAdapter(Context context, int resourceId, List<Persona> objects) {
        super(context, resourceId, objects);
        resource = resourceId;
        inflater = LayoutInflater.from(context);
    }
    private static class ViewHolder {
        TextView nome;
        TextView cognome;
        TextView numero;

    }
    @Override
    public View getView(int position, View v, ViewGroup parent) {
        Persona persona = getItem(position);
        ViewHolder viewHolder;
        final View result;
        if (v == null) {
            viewHolder = new ViewHolder();
            LayoutInflater inflater = LayoutInflater.from(getContext());
            v = inflater.inflate(R.layout.list_item, null);
            viewHolder.nome = (TextView) v.findViewById(R.id.nome);
            viewHolder.cognome = (TextView) v.findViewById(R.id.cognome);
            viewHolder.numero = (TextView) v.findViewById(R.id.numero);


            result=v;

            v.setTag(viewHolder);
        } else {
            viewHolder = (ViewHolder) v.getTag();
            result=v;
        }


        viewHolder.nome.setText(persona.getNome());
        viewHolder.cognome.setText(persona.getCognome());
        viewHolder.numero.setText(persona.getNumero());





        return v;
    }
}

XML 代码

<LinearLayout xmlns:android= "http://schemas.android.com/apk/res/android"
    xmlns:tools= "http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:padding="10dp"
    tools:context=".MainActivity"
    >
    <RelativeLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content">

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_alignParentLeft="true"
            android:layout_marginTop="15dp"
            android:layout_marginLeft="-2dp"
            android:text="Left Side"
            android:textSize="15sp"
            android:textStyle="bold" />

        <EditText
            android:id="@+id/nome"
            android:layout_width="200dp"
            android:layout_height="wrap_content"
            android:layout_alignParentStart="true"

            android:layout_alignParentRight="true"
            android:layout_marginStart="67dp"

            android:layout_marginRight="124dp"
            android:hint="New item"
            android:text=""
            android:textSize="15sp" />

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_alignParentLeft="true"
            android:layout_marginLeft="0dp"
            android:layout_marginTop="50dp"
            android:text="Left Side"
            android:textSize="15sp"
            android:textStyle="bold" />

        <EditText
            android:id="@+id/cognome"
            android:layout_width="200dp"
            android:layout_height="wrap_content"
            android:layout_alignParentStart="true"
            android:layout_alignParentRight="true"
            android:layout_marginStart="67dp"
            android:layout_marginTop="40dp"

            android:layout_marginRight="124dp"
            android:hint="New item"
            android:text=""
            android:textSize="15sp" />
        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_alignParentLeft="true"
            android:layout_marginTop="90dp"
            android:layout_marginLeft="-2dp"
            android:text="Left Side"
            android:textSize="15sp"
            android:textStyle="bold" />

        <EditText
            android:id="@+id/numero"
            android:layout_width="200dp"
            android:layout_height="wrap_content"
            android:layout_alignParentStart="true"
            android:layout_alignParentEnd="true"
            android:layout_alignParentRight="true"
            android:layout_marginStart="67dp"

            android:layout_marginTop="80dp"
            android:layout_marginEnd="125dp"
            android:layout_marginRight="124dp"
            android:hint="New item"
            android:text=""
            android:textSize="15sp" />

    </RelativeLayout>

    <Button
        android:id="@+id/btAdd"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"

        android:layout_marginLeft="35dp"
        android:gravity="bottom"
        android:text="Inserisci" />

    <ListView
        android:id="@+id/list"
        android:layout_width="match_parent"
        android:layout_height="wrap_content">
    </ListView>

</LinearLayout>

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical" android:layout_width="match_parent"
    android:layout_height="match_parent">
    <TextView
        android:id="@+id/txtview"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />

</LinearLayout>

FATAL EXCEPTION: main
    Process: com.example.listviewadd, PID: 17994
    java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference
        at com.example.listviewadd.CustomAdapter.getView(CustomAdapter.java:57)
        at android.widget.AbsListView.obtainView(AbsListView.java:2366)
        at android.widget.ListView.measureHeightOfChildren(ListView.java:1408)
        at android.widget.ListView.onMeasure(ListView.java:1315)
        at android.view.View.measure(View.java:23169)
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6749)
        at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1535)
        at android.widget.LinearLayout.measureVertical(LinearLayout.java:825)
        at android.widget.LinearLayout.onMeasure(LinearLayout.java:704)
        at android.view.View.measure(View.java:23169)
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6749)
        at android.widget.FrameLayout.onMeasure(FrameLayout.java:185)
        at androidx.appcompat.widget.ContentFrameLayout.onMeasure(ContentFrameLayout.java:143)
        at android.view.View.measure(View.java:23169)
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6749)
        at androidx.appcompat.widget.ActionBarOverlayLayout.onMeasure(ActionBarOverlayLayout.java:403)
        at android.view.View.measure(View.java:23169)
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6749)
        at android.widget.FrameLayout.onMeasure(FrameLayout.java:185)
        at android.view.View.measure(View.java:23169)
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6749)
        at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1535)
        at android.widget.LinearLayout.measureVertical(LinearLayout.java:825)
        at android.widget.LinearLayout.onMeasure(LinearLayout.java:704)
        at android.view.View.measure(View.java:23169)
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6749)
        at android.widget.FrameLayout.onMeasure(FrameLayout.java:185)
        at com.android.internal.policy.DecorView.onMeasure(DecorView.java:716)
        at android.view.View.measure(View.java:23169)
        at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:2718)
        at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1572)
        at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1855)
        at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1460)
        at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:7183)
        at android.view.Choreographer$CallbackRecord.run(Choreographer.java:949)
        at android.view.Choreographer.doCallbacks(Choreographer.java:761)
        at android.view.Choreographer.doFrame(Choreographer.java:696)
        at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:935)
        at android.os.Handler.handleCallback(Handler.java:873)
        at android.os.Handler.dispatchMessage(Handler.java:99)
        at android.os.Looper.loop(Looper.java:193)
        at android.app.ActivityThread.main(ActivityThread.java:6669)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858)

Answer 1

首先创建一个java类Person，如下所示:

class Person{
 String firstName;
 String surName;
 String phoneNumber;
}

而不是使用 ArrayAdapter<String> adapter使用 List<Person> 创建自定义适配器.

按照以下教程创建自定义适配器 https://www.journaldev.com/10416/android-listview-with-custom-adapter-example-tutorial