Question

在我的程序中，java 类之一扩展了ListActivity ，但是代替扩展ListActivity，我 尝试扩展简单的Activity ，但获取少数错误喜欢：

类型PlayListActivity

setListAdapter（ListAdapter）未定义

PlayListActivity类型的方法 getListView（）未定义

码：

public class PlayListActivity extends Activity {
// Songs list
public ArrayList<HashMap<String, String>> songsList = new ArrayList<HashMap<String, String>>();

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    setContentView(R.layout.activity_playlist);

    ArrayList<HashMap<String, String>> songsListData = new ArrayList<HashMap<String, String>>();

    SongsManager plm = new SongsManager();
    // get all songs from sdcard
    this.songsList = plm.getPlayList();

    // looping through playlist
    for (int i = 0; i < songsList.size(); i++) {
        // creating new HashMap
        HashMap<String, String> song = songsList.get(i);

        // adding HashList to ArrayList
        songsListData.add(song);
    }

    // Adding menuItems to ListView
    ListAdapter adapter = new SimpleAdapter(this, songsListData,
            R.layout.activity_playlist_item, new String[] { "songTitle" }, new int[] {
                    R.id.songTitle });

    setListAdapter(adapter);

    // selecting single ListView item
    ListView lv = getListView();
    // listening to single listitem click
    lv.setOnItemClickListener(new OnItemClickListener() {

        @Override
        public void onItemClick(AdapterView<?> parent, View view,
                int position, long id) {

        }
    });
}

activity_playlist_item.xml;

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/RelativeLayout1"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:padding="5dp" >

    <TextView
        android:id="@+id/songTitle"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_toLeftOf="@+id/imageView1"
        android:layout_toRightOf="@+id/thumbnail"
        android:maxLines="1"
        android:textColor="#ffffff"
        android:textSize="20sp"
        android:typeface="sans" />

</RelativeLayout>

activity_playlist.xml;

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    >

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

</RelativeLayout>

我正在为学习者提供 解决方案 [例如：我]，请参阅以下内容：

// declare listview globally
ListView lv ;
// reference to ListView
lv = (ListView) findViewById(R.id.list);
// set list adapter to ListView
lv.setAdapter(adapter);

并且还要改变

<ListView 
         android:id="@+id/list" .... />

谢谢到@Raghunandan＆amp; @SimplePlan用于指南！

Answer 1

方法setListAdapter（ListAdapter）未定义类型 PlayListActivity

setListAdapter是ListActivity的方法。

http://developer.android.com/reference/android/app/ListActivity.html#setListAdapter(android.widget.ListAdapter)

getListView（）方法未定义为PlayListActivity类型

getListView()是ListActivity的方法。

http://developer.android.com/reference/android/app/ListActivity.html#getListView()

而不是

setListAdapter(adapter);

// selecting single ListView item
ListView lv = getListView();

更改为

 ListView lv = (ListView) findViewById(R.id.list);
 lv.setAdapter(adapter);

更改为

 <ListView 
     android:id="@+idlist"

Answer 2

如果您延伸ListActivity，则在XML中定义ListView，如下所示，并实施getListView() ListActivity方法。

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

如果您扩展Activity，则会在XML中定义您的ListView，如下所示，无需为此实施getListView()。

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

您也初步确定了ListView

 ListView lv = (ListView) findViewById(R.id.list);
 lv.setAdapter(adapter);

如何使用Activity而不是ListActivity扩展Class

2 个答案: