ListPopupWindow 项目未正确绘制

Question

我有一个 ListPopupWindow，它是从自定义适配器填充的。自定义 xml 由 2 个文本视图和一个 LinearLayout 组成。自定义适配器填充文本视图并实例化一个自定义视图，该视图绘制缩略图大小的基于矢量的图形。然后将自定义视图添加到线性布局中。

问题是显示的第一行总是显示错误的图形。有时是另一行的图形，有时一半是正确的图形，一半是错误的行。我还注意到，如果列表中有足够的行可以滚动，则列表底部的项目在滚动时也会出现相同的问题。

还有其他人经历过吗？

自定义列表适配器：

public class PageSearchListAdapter extends SimpleCursorAdapter
{
    int _height = 130;
  int _width = 130;

  Cursor c;
  Context context;

  // Constructor, here we store any parameters we need in class variables 
  //
    public PageSearchListAdapter(Context context, 
                                 int layout, 
                                 Cursor c,
                                 String[] from, 
                                 int[] to) 
    {
        super(context, layout, c, from, to);

    this.c = c;
    this.context=context;

    }

    // Main view method - the views in query_list_item are populated here
    //
  @Override
  public View getView(int position, View convertView, ViewGroup parent) 
  {
    // Make sure we have a view to work with
    //
    if(convertView == null)
        convertView = View.inflate(context, R.layout.query_list_item, null);

    View row = convertView; 

    // go to the correct row in the cursor
    //
    c.moveToPosition(position);

    // Get the views that need populating
    //
    TextView PageNum = (TextView) convertView.findViewById(R.id.Page_Num);
    LinearLayout pic = (LinearLayout) convertView.findViewById(R.id.Page_Canvas);
    TextView Date = (TextView) convertView.findViewById(R.id.Page_Date);

    // Set the values
    //
    PageNum.setText(c.getString(c.getColumnIndex("PageNum")));
    Date.setText(c.getString(c.getColumnIndex("Timestamp")));

    List<Point> Vectors = new ArrayList<Point>();

    byte[] asBytes = c.getBlob(c.getColumnIndex("Vectors"));

    ..
    .. removed code to Convert Blob to array of 'Vector' records ...
    ..

    // Draw the page
    //

    NotePadPage npPage = new NotePadPage(context, Vectors);

    npPage.setLayoutParams(new LayoutParams(_width, _height));

    pic.addView(npPage);

    return(row);
  }

}

NotePadPage 类：

    // Adapter to display a custom list item in a list view
    //
    public class NotePadPage extends View
    {

        int _height = 130;
        int _width = 130;

        Bitmap _bitmap;
        Canvas _canvas;

        Paint _paint;

        List<Point> _Vectors = new ArrayList<Point>();


        public NotePadPage(Context context, List<Point> Vectors) 
        {
            super(context);

            _Vectors = Vectors;

            _paint = new Paint();
            _paint.setColor(Color.WHITE);
            _paint.setStyle(Paint.Style.STROKE);

        }

        @Override
        protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) 
        {
            _height = View.MeasureSpec.getSize(heightMeasureSpec);
            _width = View.MeasureSpec.getSize(widthMeasureSpec);

            setMeasuredDimension(_width, _height);

            _bitmap = Bitmap.createBitmap(_width, _height, Bitmap.Config.ARGB_8888);
            _canvas = new Canvas(_bitmap);        
        }

        @Override
        protected void onDraw(Canvas canvas) 
        {
            float yRatio = 1092/ _height;
            float xRatio = 800 / _width;

            Point lastPoint = null;

            for (Point point : _Vectors) 
            {
                switch (point.Type)
                {
                    case Start:
                    {
                        lastPoint = point;
                        break;
                    }
                    case Midpoint:
                    case End:
                    {
                        canvas.drawLine(lastPoint.x / xRatio, lastPoint.y/ yRatio, point.x / xRatio, point.y/ yRatio, _paint);
                        lastPoint = point;                  
                    }
                }
            }

        }    

    }

引用类：

    public class Point 
    {
        public float x, y;

        public PointType Type;      
    }

    public enum PointType 
    { 
        Start, 
        Midpoint , 
        End;

    }

列表行的 XML：

    <?xml version="1.0" encoding="utf-8"?>
    <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent" 
        android:gravity="center_vertical|center_horizontal"    >

        <TextView        
            android:id="@+id/Page_Num"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:gravity="center_vertical|center_horizontal"
            android:layout_marginRight="5dp"        
            android:text="1"
            android:textAppearance="?android:attr/textAppearanceMedium" />

        <LinearLayout
            android:id="@+id/Page_Canvas"
            android:layout_width="130dip"
            android:layout_height="130dip"
            android:gravity="center_vertical|center_horizontal"
            android:layout_toRightOf="@id/Page_Num">
        </LinearLayout>    

        <TextView
            android:id="@+id/Page_Date"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:gravity="center_vertical|center_horizontal"
            android:layout_marginLeft="5dp"        
            android:text="Medium Text"
            android:textAppearance="?android:attr/textAppearanceMedium" 
            android:layout_toRightOf="@id/Page_Canvas">

        </TextView>

    </RelativeLayout>