Question

我正在尝试实现一个自定义SimpleCursorAdapter，以便在ListView中切换布局，但滚动时我会得到非常随机的结果。

我的问题是，当我向上和向下滚动时，ListView看似随机，混合布局。例如，一行可以首先具有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的工作原理。我已经成功地使用bindView来确定我是否要在布局中隐藏图像，但是新的View在黑暗中隐藏了我的实现以及列表滚动的行为方式。

我的目标是拥有一个包含x个项目的列表。根据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来实现它。 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>

使用上述布局的精简片段：

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);
    }
}
}

Answer 1

在阅读了你的问题和代码之后，我认为你应该知道无论何时向上或向下滚动列表视图，它都会与适配器通信以填充进入焦点的新项目以及针对不同数据的不同行的情况应该制作一个arraylist，其中包含背景不同的项目的名称或ID，然后在每次调用适配器时根据需要开始制作背景。

为什么我的自定义SimpleCursorAdapter在ListView滚动时返回不同的结果

1 个答案: