Question

基于一个例子我试图创建一个显示自定义ListItems的ListView。我用XML定义ListItem：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="?android:attr/listPreferredItemHeight"
    android:padding="6dip" >

    <ImageView
        android:id="@+id/icon"
        android:layout_width="wrap_content"
        android:layout_height="fill_parent"
        android:layout_alignParentBottom="true"
        android:layout_alignParentTop="true"
        android:layout_marginRight="6dip"
        android:contentDescription="TODO"
        android:src="@drawable/icon" />

    <TextView
        android:id="@+id/secondLine"
        android:layout_width="fill_parent"
        android:layout_height="26dip"
        android:layout_alignParentBottom="true"
        android:layout_alignParentRight="true"
        android:layout_toRightOf="@id/icon"
        android:ellipsize="marquee"
        android:singleLine="true"
        android:text="Description"
        android:textSize="12sp" />

    <TextView
        android:id="@+id/firstLine"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_above="@id/secondLine"
        android:layout_alignParentRight="true"
        android:layout_alignParentTop="true"
        android:layout_alignWithParentIfMissing="true"
        android:layout_toRightOf="@id/icon"
        android:gravity="center_vertical"
        android:singleLine="true"
        android:text="Example application"
        android:textSize="16sp" />

</RelativeLayout>

我创建了一个类来保存ListItem中显示的数据：

public class UserRecord {
    public String username;
    public String email;

    public UserRecord(String username, String email) {
        this.username = username;
        this.email = email;
    }
}

我还有一个自定义ArrayAdapter：

public class UserItemAdapter extends ArrayAdapter<UserRecord> {
    private ArrayList<UserRecord> users;
    public LayoutInflater vi;
    private Context context;

    public UserItemAdapter(Context context, int textViewResourceId, ArrayList<UserRecord> users) {
        super(context, textViewResourceId, users);
        this.users = users;
        this.context = context;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        View v = convertView;
        if (v == null) {
            LayoutInflater vi = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            v = vi.inflate(R.layout.listitem, null);
        }

        UserRecord user = users.get(position);
        if (user != null) {
            TextView username = (TextView) v.findViewById(R.id.firstLine);
            TextView email = (TextView) v.findViewById(R.id.secondLine);

            Log.v(TAG, "user " + user.username);
            Log.v(TAG, "mail " + user.email);
            if (username != null) {
                Log.v(TAG, "username NOT null");
                username.setText("user " + user.username);
            }

            if (email != null) {
                Log.v(TAG, "email NOT null");
                email.setText("Email: " + user.email);
            }
        }
        return v;
    }
}

初始化：

ArrayList<UserRecord> appointment;
UserItemAdapter aa;
ListView lv;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    lv = (ListView) findViewById(R.id.listView1);

    b1 = (Button) findViewById(R.id.button1);
    b1.setOnClickListener(this);

    appointment = new ArrayList<UserRecord>();
    aa = new UserItemAdapter(this, android.R.layout.simple_list_item_1, appointment);
    lv.setAdapter(aa);

}

最后，当我按下按钮时：

public void onClick(View v) {

    if (v == b1) {
        UserRecord ur = new UserRecord("User " + i, "mail@mail.net");
        Log.v(TAG, "button 1 " + i);
        aa.add(ur);
    } else {
        Log.v(TAG, "unknown");
    }
}

问题是显示“电子邮件”，但“用户名”没有显示，虽然处理方式相同，但我认为没有区别。此外，还应该设置应该设置的if（）。

有没有人对错误提示？

祝你好运托

Answer 1

我可能会弄错，但我几乎肯定你应该这样做：

public void onClick(View v) {

    if (v == b1) {
        UserRecord ur = new UserRecord("User " + i, "mail@mail.net");
        Log.v(TAG, "button 1 " + i);
        users.add(ur);
    } else {
        Log.v(TAG, "unknown");
    }
}

而不是：

public void onClick(View v) {

    if (v == b1) {
        UserRecord ur = new UserRecord("User " + i, "mail@mail.net");
        Log.v(TAG, "button 1 " + i);
        aa.add(ur);
    } else {
        Log.v(TAG, "unknown");
    }
}

我从来没有在我的ADAPTER类中添加一个项目，但总是添加到对象的LIST中。在这种情况下，“用户”而不是“aa”。

Answer 2

问题出在listitem.xml文件中。尝试改为：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="?android:attr/listPreferredItemHeight"
android:padding="6dip" >

<ImageView
    android:id="@+id/icon"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignParentTop="true"
    android:layout_marginRight="6dip"
    android:contentDescription="TODO"
    android:src="@drawable/icon" />


<TextView
    android:id="@+id/firstLine"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:layout_alignParentTop="true"
    android:layout_toRightOf="@id/icon"
    android:gravity="center_vertical"
    android:text="Example application"
    android:textSize="16sp" />

<TextView
    android:id="@+id/secondLine"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:layout_toRightOf="@id/icon"
    android:ellipsize="marquee"
    android:text="Description"
    android:layout_below="@id/firstLine"
    android:textSize="12sp" />

</RelativeLayout>

Answer 3

更改此

aa = new UserItemAdapter(this, android.R.layout.simple_list_item_1, appointment);

对此;

aa = new UserItemAdapter(this, R.layout.listitem, appointment);

试试这个：

public void onClick(View v) {

    if (v == b1) {
        UserRecord ur = new UserRecord("User " + i, "mail@mail.net");
        Log.v(TAG, "button 1 " + i);
        appointment.add(ur);
        aa.notifyDataSetChanged(); 
    } else {
        Log.v(TAG, "unknown");
    }
}

Android ListView：自定义ListItem无法正确显示

3 个答案: