我正在尝试实现自定义 SimpleCursorAdapter 以切换 ListView 中的布局，但滚动时得到非常随机的结果。
我的问题是，当我上下滚动时，ListView 似乎是随机的，混淆了布局。例如，一行一开始可以有 listview_item_row 布局，但是当滚动进出屏幕时，它可以被 listview_item_reply_row 替换并再次返回。我不能说我真的了解 newView 是如何工作的。我已经成功地能够使用 bindView 来确定我是否要在布局中隐藏图像，但是对于它的实现以及为什么列表滚动的行为方式，新视图对我来说是黑暗的。
我的目标是有一个包含 x 个项目的列表。根据该项目是回复还是新消息，我想在该行上加载特定布局。根据行是否有图像，我想在行布局中显示/隐藏图像视图。
我在代码中省略的是导入和行布局。我正在尝试通过在 v4 支持包中使用 Fragments 和 SimpleCursorAdapter 来实现这一点。ListFragment 的行布局明显不同，但包含相同的小部件。
ListView 布局：
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical" >
<TextView
android:id="@+id/text_feed_header_random"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:gravity="center_vertical|center_horizontal"
android:padding="4dp"
android:text="Allmänt"
android:textAppearance="?android:attr/textAppearanceMedium"
android:textColor="#FFF" />
<!--
The frame layout is here since we will be showing either
the empty view or the list view.
-->
<FrameLayout
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:layout_below="@id/text_feed_header_random"
android:layout_above="@+id/footer" >
<!--
Here is the list. Since we are using a ListActivity, we
have to call it "@android:id/list" so ListActivity will
find it
-->
<ListView
android:id="@android:id/list"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:drawSelectorOnTop="false" />
<!-- Here is the view to show if the list is emtpy -->
<TextView
android:id="@android:id/empty"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:text="No items."
android:textAppearance="?android:attr/textAppearanceMedium" />
</FrameLayout>
<LinearLayout
android:id="@+id/footer"
style="@android:style/ButtonBar"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:orientation="horizontal" >
<Button
android:id="@+id/button_random_post"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="Gör ett inlägg!" />
<Button
android:id="@+id/button_random_refresh"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="Refresh list!" />
</LinearLayout>
</RelativeLayout>
使用上述布局的浓缩片段：
public class RandomFragment extends ListFragment implements LOG {
private DatabaseHelper mDbHelper;
private KarenfeedCursorAdapter mAdapter;
private Cursor mCursor;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
Log.d(TAG, "RANDOMFRAGMENT START!");
mDbHelper = new DatabaseHelper(getActivity());
mDbHelper.open();
mDbHelper.setTable(Posts.TABLE_RANDOM_POSTS);
//TODO: Replace SimpleCursorAdapter with a FragmentList instead...
mCursor = mDbHelper.getAllPostsSortedCursor();
String[] columns = { Posts.COLUMN_ID, Posts.COLUMN_CREATED, Posts.COLUMN_USER, Posts.COLUMN_COMMENT };
int[] to = { R.id.imageItemPhoto, R.id.textItemDate, R.id.textItemUser, R.id.textItemComment };
int flags = 0;
mAdapter = new FeedCursorAdapter(getActivity(), R.layout.listview_item_row, mCursor, columns, to, flags);
this.setListAdapter(mAdapter);
initFeedList(); // This call in the end executes mCursor = mDbHelper.getAllPostsSorted(); mAdapter.changeCursor(mCursor); mAdapter.notifyDataSetChanged();
}
}
ListFragment 连接到的 SimpleCursorAdapter：
public class FeedCursorAdapter extends SimpleCursorAdapter implements LOG {
private Context mContext;
private int mLayout;
public FeedCursorAdapter(Context context, int layout, Cursor c, String[] from, int[] to, int flags) {
super(context, layout, c, from, to, flags);
// TODO Auto-generated constructor stub
mContext = context;
mLayout = layout;
}
@Override
public View newView(Context context, Cursor cursor, ViewGroup parent) {
LayoutInflater inflater = LayoutInflater.from(context);
View view;
int id = cursor.getInt(cursor.getColumnIndex(Posts.COLUMN_ID));
int parentId = cursor.getInt(cursor.getColumnIndex(Posts.COLUMN_PARENT_ID));
Log.d(TAG, "id: " +id+ " parentId: " +parentId);
int hasImage = cursor.getInt(cursor.getColumnIndex(Posts.COLUMN_IMAGE));
if(id == parentId) {
view = inflater.inflate(R.layout.listview_item_row, parent, false);
} else {
view = inflater.inflate(R.layout.listview_item_reply_row, parent, false);
}
return view;
}
@Override
public void bindView(View view, Context context, Cursor cursor) {
Log.d(TAG, "bindView()");
int id = cursor.getInt(cursor.getColumnIndex(Posts.COLUMN_ID));
int parentId = cursor.getInt(cursor.getColumnIndex(Posts.COLUMN_PARENT_ID));
int hasImage = cursor.getInt(cursor.getColumnIndex(Posts.COLUMN_IMAGE));
String date = cursor.getString(cursor.getColumnIndex(Posts.COLUMN_CREATED));
String user = cursor.getString(cursor.getColumnIndex(Posts.COLUMN_USER));
String comment = cursor.getString(cursor.getColumnIndex(Posts.COLUMN_COMMENT));
TextView dateView = (TextView) view.findViewById(R.id.textItemDate);
TextView userView = (TextView) view.findViewById(R.id.textItemUser);
TextView commentView = (TextView) view.findViewById(R.id.textItemComment);
ImageView imageView = (ImageView) view.findViewById(R.id.imageItemPhoto);
dateView.setText(date);
userView.setText(user);
commentView.setText(comment);
if(hasImage == 0) {
imageView.setVisibility(ImageView.GONE);
} else {
String bitmapPath = Environment.getExternalStorageDirectory().getPath() + "/feed/" + id + "_thumb.jpg";
Bitmap bitmap = BitmapFactory.decodeFile(bitmapPath);
BitmapDrawable bitmapDrawable = new BitmapDrawable(bitmap);
imageView.setImageDrawable(bitmapDrawable);
imageView.setVisibility(ImageView.VISIBLE);
}
}
}