1

我有一个Apple有两个字段的类，colour和rotation，以及一个AppleViewView ，它以该颜色绘制苹果并在其onDraw方法中旋转（这是我实际代码的简化）。AppleView 有一个可以重新分配的默认苹果（比如说，红色并旋转 0 度）。这是这两个类的一些伪代码：

public class Apple {
    int colour;
    int rotation;
}

public class AppleView extends View {
    Apple apple = getDefaultApple();

    @Override
    protected void onDraw(Canvas canvas) {
        drawApple(canvas, apple);
    }
}

我想从苹果的 ArrayList 中制作 AppleViews 的 ListView。我创建了两个布局：一个 ListView ( R.layout.list_view)：

<?xml version="1.0" encoding="utf-8"?>
<ListView xmlns:android="http://schemas.android.com/apk/res/android"
          android:layout_width="match_parent"
          android:layout_height="match_parent"
          android:id="@android:id/list">
</ListView>

和一个列表项，它只是一个AppleView( R.layout.list_item)：

<?xml version="1.0" encoding="utf-8"?>
<com.mypackage.AppleView xmlns:android="http://schemas.android.com/apk/res/android"
      android:layout_width="match_parent"
      android:layout_height="match_parent"
      android:id="@+id/apple">
</com.mypackage.AppleView>

最后，我扩展ListActivity并使用自定义适配器类来绘制列表项：

public class MyListActivity extends ListActivity {

    ArrayList<Apple> apples = new ArrayList<Apple>();

    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.list_view);

        // Add 100 random apples to the list for demonstration.
        for (int i = 0; i < 100; i++) {
            apples.add(getRandomApple());
        }

        getListView().setAdapter(new MyAdapter(this, R.layout.list_item, apples));
    }

    class MyAdapter extends ArrayAdapter<Apple> {
        public MyAdapter(Context context, int resourceID, ArrayList<Apple> items) {
            super(context, resourceID, items);
        }

        @Override
        public View getView(int position, View convertView, ViewGroup parent) {

            if (convertView == null) {
                convertView = getLayoutInflater().inflate(R.layout.list_item, parent, false);
            }

            // Change this AppleView's apple to the new ArrayList element at this position.
            AppleView appleView = (AppleView) convertView.findViewById(R.id.apple);
            appleView.apple = apples.get(position);

            return convertView;
        }
    }
}

尽管调用了所有正确的方法（即每个苹果的 getView 和 onDraw），但 ListView 不显示：

在此处输入图像描述

上面代码的错误在哪里？

4

2 回答 2

0

设置为的 ListView 元素的高度match_parent未定义（即为 0），因为高度由内容的大小决定。要解决此问题，请为元素指定固定高度，例如：

<?xml version="1.0" encoding="utf-8"?>
<com.mypackage.AppleView xmlns:android="http://schemas.android.com/apk/res/android"
      android:layout_width="match_parent"
      android:layout_height="100dp" /* THIS LINE CHANGED */
      android:id="@+id/apple">
</com.mypackage.AppleView>
于 2013-09-15T04:41:02.890 回答
0 
I have made some change with your arrayadapter.
 class MyAdapter extends ArrayAdapter<ArrayList<Apple>> {
        private ArrayList<Apple> apple = null;
        public MyAdapter(Context context, int resourceID, ArrayList<Apple> items) {
            super(context, resourceID, items);
            this.apple = items;
        }


  @Override
        public int getCount() {
    //Check with this size if it is greater than zero,then list is visible
            return apple.size();
        }


        @Override
        public View getView(int position, View convertView, ViewGroup parent) {

            if (convertView == null) {
                convertView = getLayoutInflater().inflate(R.layout.list_item, parent, false);
            }

            // Change this AppleView's apple to the new ArrayList element at this position.
            AppleView appleView = (AppleView) convertView.findViewById(R.id.apple);
            appleView.apple = apple.get(position);

            return convertView;
        }
    }
于 2013-09-27T19:32:55.623 回答