Question

我有一个关于自定义Android ListView项目的问题：

我正在学习本教程：http://codehenge.net/blog/2011/05/customizing-android-listview-item-layout/

第一部分，正常的R.android.simple_text_item_1对我来说很好，所以我在每一行都得到了带有字符串的ListView。

然后我继续尝试修改ListView的项目，如下所述：

我为列表项定义了这个XML数据。它是一个只包含两个TextViews的LinearLayout

<?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="horizontal" >

<TextView
    android:id="@+id/username"
    android:layout_width="match_parent"
    android:layout_height="wrap_content" />

<TextView
    android:id="@+id/email"
    android:layout_width="match_parent"
    android:layout_height="wrap_content" />

</LinearLayout>

我定义了一个数据类UserRecord，它简单地给了我创建包含名称和电子邮件地址的对象的能力

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

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

我复制了整个适配器类，但我收到一个错误，我评论的行

public class UserItemAdapter extends ArrayAdapter<UserRecord> {
private ArrayList<UserRecord> users;

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

@Override
public View getView(int position, View convertView, ViewGroup parent) {
    View v = convertView;
    if (v == null) {
    //In the following line I get the error: "The method getSystemService is undefined
    //for type UserItemAdapter
    LayoutInflater vi = (LayoutInflater)getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    v = vi.inflate(R.layout.list_item, null);
    }

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

    if (username != null) {
        username.setText(user.username);
    }

    if(email != null) {
        email.setText("Email: " + user.email );
    }
}
return v;
}
}

我在MainActivity中改变了我的onCreate方法，如下所示，也许这就是错误。

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

ArrayList<UserRecord> users = new ArrayList<UserRecord>();
UserRecord a = new UserRecord("a","b");
users.add(a);

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

//The following adapter worked fine when using a String array
//listView.setAdapter(new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, items));

//This adapter doesn't work I guess :(
listView.setAdapter(new UserItemAdapter(this, R.layout.list_item, users));

}

谁能告诉我，我的错在哪里？如果我尝试启动我的应用程序，它甚至没有启动，我的模拟器说“不幸的是关闭了blabla”。 -.-

Answer 1

LayoutInflater是一个systemService，用于扩展布局，例如列表项的布局。为了访问任何系统服务，你需要一些上下文时间。然后尝试这个。

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

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

@Override
public View getView(int position, View convertView, ViewGroup parent) {
View v = convertView;
if (v == null) {
//In the following line I get the error: "The method getSystemService is undefined
//for type UserItemAdapter
LayoutInflater vi = (LayoutInflater)context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
v = vi.inflate(R.layout.list_item, null);
}

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

if (username != null) {
    username.setText(user.username);
}

if(email != null) {
    email.setText("Email: " + user.email );
}
}
return v;
}
}

自定义android ListView项目

1 个答案: