Question

我对Android很新，我正在尝试创建一个列表视图，它将显示我创建的类的详细信息

我的活动是：

public class UserList extends ListActivity {

private ListView lv;
private ArrayList<Player> players;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_user_list);
    lv = (ListView) findViewById(R.id.UserListView);
    this.players = new ArrayList<Player>();
    this.players.add(new Player("AAAA"));
    this.players.add(new Player("BBBB"));
    PlayerAdapter pa = new PlayerAdapter(this, R.layout.userlist_list_item, this.players);
    lv.setAdapter(pa);
}

我的适配器是这样的：

public class PlayerAdapter extends ArrayAdapter<Player> {

private ArrayList<Player> players;
private Context context;

public PlayerAdapter(Context context, int textViewResourceId,
        ArrayList<Player> players) {
    super(context, textViewResourceId, players);
    // TODO Auto-generated constructor stub
    this.players = players;
    this.context = context;
}

@Override
public View getView(int position, View convertView, ViewGroup parent) {
    if (convertView == null) {
        LayoutInflater vi = (LayoutInflater) context
                .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        convertView = vi.inflate(R.layout.userlist_list_item, null);
    }
    Player p = players.get(position);
    TextView name = (TextView) convertView.findViewById(R.id.ListNameData);
    name.setText(p.getName());
    TextView money = (TextView)convertView.findViewById(R.id.ListMoneyData);
    money.setText(""+p.getCurrentmoney());
    TextView exp = (TextView)convertView.findViewById(R.id.ListExpData);
    exp.setText(""+p.getExp());

    return convertView;
}

活动XML只有一个列表视图，列表项XML是这样的：

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:baselineAligned="false"
android:orientation="horizontal"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin" >

<LinearLayout
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_weight="0.5"
    android:orientation="vertical" >

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal" >

        <TextView
            android:id="@+id/ListNameTextView"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginTop="10dp"
            android:textStyle="bold"
            android:textSize="15sp"
            android:text="@string/username" />

        <TextView
            android:id="@+id/ListNameData"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="" />
    </LinearLayout>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content" >

        <TextView
            android:id="@+id/ListMoneyTextView"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginTop="10dp"
            android:textStyle="bold"
            android:textSize="15sp"
            android:text="@string/money" />

        <TextView
            android:id="@+id/ListMoneyData"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="" />
    </LinearLayout>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content" >

        <TextView
            android:id="@+id/ListEXPTextView"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginTop="10dp"
            android:textStyle="bold"
            android:textSize="15sp"
            android:text="@string/expList" />

        <TextView
            android:id="@+id/ListExpData"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="" />
    </LinearLayout>
</LinearLayout>

<LinearLayout
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_weight="0.5"
    android:orientation="vertical" >

    <Button
        android:id="@+id/ListSwitchTo"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="right"
        android:text="@string/switchto" />

    <Button
        android:id="@+id/ListDeleteUser"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="right"
        android:text="@string/deleteuser" />
</LinearLayout>

我的堆栈跟踪：

[2014-07-10 20:34:25 - ddms] null
java.lang.NullPointerException
at org.eclipse.debug.internal.ui.DebugUIPlugin.launchInBackground(DebugUIPlugin.java:1286)
at org.eclipse.debug.ui.DebugUITools.launch(DebugUITools.java:753)
at      com.android.ide.eclipse.adt.internal.launch.AndroidLaunchController.debugRunningApp(AndroidLaunchController.java:178)
at com.android.ide.eclipse.adt.internal.launch.AndroidLaunchController.clientChanged(AndroidLaunchController.java:1749)
at com.android.ddmlib.AndroidDebugBridge.clientChanged(AndroidDebugBridge.java:926)
at com.android.ddmlib.Device.update(Device.java:774)
at com.android.ddmlib.Client.update(Client.java:903)
at com.android.ddmlib.HandleWait.handleWAIT(HandleWait.java:88)
at com.android.ddmlib.HandleWait.handleChunk(HandleWait.java:66)
at com.android.ddmlib.MonitorThread.callHandler(MonitorThread.java:414)
at com.android.ddmlib.MonitorThread.processClientActivity(MonitorThread.java:322)
at com.android.ddmlib.MonitorThread.run(MonitorThread.java:263)

它立即崩溃，我无法弄清楚如何解决它。感谢您阅读并希望帮助我

Answer 1

好的，您的问题出在您的适配器中。问题出在您的convertView上;您创建了一个新视图v，这是您期望使用的视图。相反，您使用始终为null的convertView。这会导致NPE或NullPointerException被抛出。

简单的解决方案就是放弃v。您实际上不需要为通用视图创建新名称; convertView可以正常使用。或者，您可以在v充气后将convertView分配给v。

Answer 2

你可以使用baseadaper轻松工作。看这个例子

[http://theopentutorials.com/tutorials/android/listview/android-custom-listview-with-image-and-text-using-baseadapter/]

使用自定义适配器进行列表视图

2 个答案: