android - 上下滚动时加载程序不会停止向列表项添加 View

Question

我尝试使用自定义 CursorLoader 将 ListView 项加载到列表中。问题是，如果我滚动到底部并再次向上滚动，Android 会向每个列表项添加多个新图像。我的问题是，如何防止 Android 将更多图像加载到列表中。
第 1 列应该始终只有一张图片，第 2 列应该始终只有两张图片...

主.java

public class Main extends FragmentActivity
    implements LoaderManager.LoaderCallbacks<Cursor> {

private Context mCtx       = null;
private MyAdapter mAdapter = null;

private final static String COLUMN_A = "a";

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    mCtx     = this;
    mAdapter = new MyAdapter(mCtx);

    ((ListView) findViewById(R.id.listview)).setAdapter(mAdapter);
    getSupportLoaderManager().initLoader(0, null, this);
}


@Override
public Loader<Cursor> onCreateLoader(int loader_id, Bundle bundle) {

    return new MyCursorLoader(mCtx) {

        @Override
        public Cursor loadInBackground() {
            MatrixCursor m = new MatrixCursor(new String[]{"_id", COLUMN_A});
            m.addRow(new String[]{"1", "Column 1"});
            m.addRow(new String[]{"2", "Column 2"});
            m.addRow(new String[]{"3", "Column 3"});
            m.addRow(new String[]{"4", "Column 4"});
            m.addRow(new String[]{"5", "Column 5"});
            return m;
        }
    };
}

@Override
public void onLoadFinished(Loader<Cursor> loader, Cursor c) {
    mAdapter.changeCursor(c);
}

@Override
public void onLoaderReset(Loader<Cursor> loader) {
    mAdapter.changeCursor(null);
}


private class MyAdapter extends CursorAdapter {
    private final LayoutInflater mInflater;

    public MyAdapter(final Context ctx) {
        super(ctx, null, 0);
        mInflater = LayoutInflater.from(ctx);
    }

    @Override
    public View newView(Context ctx, Cursor c, ViewGroup parent) {
        return mInflater.inflate(R.layout.item, parent, false);
    }

    @Override
    public void bindView(final View v, final Context ctx, final Cursor c) {
        LinearLayout parent = (LinearLayout) v;
        final int position = c.getPosition();

        Log.i("MyAdapter", "Cursor position: "+ position
                + "\tImages: "+ (parent.getChildCount() -1));

        ((TextView) v.findViewById(R.id.content))
            .setText(c.getString(c.getColumnIndex(COLUMN_A)));


        LinearLayout ll = new LinearLayout(ctx);
        ll.setOrientation(LinearLayout.VERTICAL);

        for (int i=0; i<(position+1); i++) {
            SystemClock.sleep(i * 100);
            ImageView img = new ImageView(ctx);
            img.setImageResource(R.drawable.ic_launcher);
            ll.addView(img);
        }

        parent.addView(ll);
    }
}


private abstract class MyCursorLoader extends CursorLoader {

    public MyCursorLoader(Context ctx) {
        super(ctx);
    }

    @Override
    public abstract Cursor loadInBackground();
}

activity_main.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context=".Main" >

    <ListView android:id="@+id/listview"
    android:layout_width="match_parent"
    android:layout_height="match_parent" >

    </ListView>

</RelativeLayout>

item.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >

    <TextView android:id="@+id/content"
    android:layout_width="match_parent"
    android:layout_height="30dip"
    android:text="---"
    />


</LinearLayout>

↓ 在 Galaxy S1 上尝试 Diogo Bento 建议后:

Answer 1

这不是一个有效的解决方案，但您可以删除 LinearLayout。一个有效的解决方案是检查 LinearLayout 是否具有与位置不同的 childs 数量，并添加或删除图像以获得所需的图像数量。

**parent.removeViewAt(1);**
LinearLayout ll = new LinearLayout(ctx);
ll.setOrientation(LinearLayout.VERTICAL);

 for (int i=0; i<(position+1); i++) {
        SystemClock.sleep(i * 100);
        ImageView img = new ImageView(ctx);
        img.setImageResource(R.drawable.ic_launcher);
        ll.addView(img);
 }
parent.addView(ll);