如何防止回收的 ListView 项目显示旧内容？

Question

我正在开发一个使用自定义 ResourceCursorAdapter 来显示 TextView 和 CheckBox 的 ListView。 TextView 和 CheckBox 从 Cursor 获取它们的状态。我遇到了一些问题，最近的一个问题是，当我滚动某些行时，有些行有来自旧 TextViews 的文本，并且在不应该选择的时候选择了一些 CheckBox。我添加了一条日志行来查看发生了什么，这让我更加困惑。

@Override
public void bindView(View v, Context ctx, Cursor c) {
    ViewHolder holder = (ViewHolder)v.getTag();

holder.tv.setText(holder.tvText);           
holder.cb.setChecked(holder.checked);
Log.d(TAG, "in bindView, rowId:" + holder.rowId + " Scripture:" + holder.tvText);   
}

.

@Override
public View newView(Context ctx, Cursor c, ViewGroup vg){       

    View v = li.inflate(layout, vg, false);
    ViewHolder holder;

    holder = new ViewHolder();
    holder.tv = (TextView)v.findViewById(to[0]);
    holder.tvText = c.getString(c.getColumnIndex(from[0]));
    holder.cb = (CheckBox)v.findViewById(to[1]);
    holder.rowId = c.getLong(c.getColumnIndex(from[2]));
    holder.checked = (c.getString(c.getColumnIndexOrThrow(from[1])).equals("n")) ?
            false : true;
    holder.cb.setOnClickListener(new OnClickListener() {
        @Override
        public void onClick(View v) {
            View rowView = ((View)v.getParent());
            ViewHolder holder = (ViewHolder)rowView.getTag();

            holder.checked = (holder.checked == false) ? true : false;

            smDb.setMemorized(holder.rowId);
            rowView.setTag(holder);
            Log.d(TAG, "check box clicked: " + holder.rowId);
        }});
    Log.d(TAG, "in newView, rowId:" + holder.rowId);
    v.setTag(holder);


    return v;       
}

.

static class ViewHolder {
    TextView tv;
    String tvText;
    CheckBox cb;
    boolean checked;
    Long rowId;
}

日志输出

in newView, rowId:26
in bindView, rowId:26 Scripture:Matthew 5:14-6
in bindView, rowId:26 Scripture:Matthew 5:14-6
in bindView, rowId:26 Scripture:Matthew 5:14-6
in bindView, rowId:26 Scripture:Matthew 5:14-6
in bindView, rowId:26 Scripture:Matthew 5:14-6
in bindView, rowId:26 Scripture:Matthew 5:14-6
in bindView, rowId:26 Scripture:Matthew 5:14-6
in bindView, rowId:26 Scripture:Matthew 5:14-6
in bindView, rowId:26 Scripture:Matthew 5:14-6
in bindView, rowId:26 Scripture:Matthew 5:14-6
in bindView, rowId:26 Scripture:Matthew 5:14-6
in newView, rowId:27
in bindView, rowId:27 Scripture:Matthew 6:24
in newView, rowId:28
in bindView, rowId:28 Scripture:Matthew 16:15-9
in newView, rowId:29
in bindView, rowId:29 Scripture:Matthew 25:40
in newView, rowId:30
in bindView, rowId:30 Scripture:Luke 24:36-9
in newView, rowId:31
in bindView, rowId:31 Scripture:John 3:5
in newView, rowId:32
in bindView, rowId:32 Scripture:John 7:17
in newView, rowId:33
in bindView, rowId:33 Scripture:John 10:16
in newView, rowId:34
in bindView, rowId:34 Scripture:John 14:15
in newView, rowId:26
in bindView, rowId:26 Scripture:Matthew 5:14-6
in bindView, rowId:26 Scripture:Matthew 5:14-6
in bindView, rowId:26 Scripture:Matthew 5:14-6
in bindView, rowId:26 Scripture:Matthew 5:14-6
in bindView, rowId:26 Scripture:Matthew 5:14-6
in bindView, rowId:26 Scripture:Matthew 5:14-6
in bindView, rowId:26 Scripture:Matthew 5:14-6
in bindView, rowId:26 Scripture:Matthew 5:14-6
in bindView, rowId:26 Scripture:Matthew 5:14-6
in bindView, rowId:26 Scripture:Matthew 5:14-6

Answer 1

这是导致您的问题的视图回收。

我不确定这是不是最顺畅的处理方式，但我就是这样做的。我创建了一个数组来保存我的按钮状态信息，然后在我的 getView 方法中使用它来确保即使元素离开屏幕也能保持状态。

我的一个项目中的示例，其中我有一个列表适配器，每行上都有按钮，可以有多种状态（文本和颜色）：

public class ButtonCursorAdapter extends SimpleCursorAdapter {
    private Cursor c;                       // Passed in cursor
    private Context context;
    private Activity activity;
    public static String[] atdState;       // String array to hold button state
    public static String[] atdRow;         // Matching string array to hold db rowId

    public ButtonCursorAdapter(Context context, int layout, Cursor c,
                    String[] from, int[] to) {
            super(context, layout, c, from, to);
            this.c = c;
            this.context = context;
            this.activity = (Activity) context;
            atdState = new String[c.getCount()];  // initialize button state array
            atdRow = new String[c.getCount()];    // initialize db rowId array
            c.moveToFirst();
            int i = 0;
            while (c.isAfterLast() == false) {
                    if (c.getString(3) == null) {  // if state is null, set to " "
                            atdState[i] = " ";
                    } else {
                            atdState[i] = c.getString(3);  // set state to state saved in db
                    }
                    atdRow[i] = c.getString(0);     // set the rowId from the db
                    i++;
                    c.moveToNext();
            }
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
            if (convertView == null)
                    convertView = View.inflate(context,
                                    R.layout.listlayoutdoublebutton, null);
            final int pos = position;
            View row = convertView;
            c.moveToPosition(position);
            TextView first = (TextView) convertView.findViewById(R.id.ListItem1);
            TextView last = (TextView) convertView.findViewById(R.id.ListItem2);
            Button atdButton = (Button) convertView.findViewById(R.id.attendbutton);
            first.setText(c.getString(1));
            last.setText(c.getString(2));
            atdButton.setText(atdState[position]);  // set the button state
            if (atdState[position].equals("P")) {   // colorize the button depending on state
                    atdButton.getBackground().setColorFilter(0xFF00FF00,
                                    PorterDuff.Mode.MULTIPLY);
            } else if (atdState[position].equals("T")) {
                    atdButton.getBackground().setColorFilter(0xFFFFFF00,
                                    PorterDuff.Mode.MULTIPLY);
            } else if (atdState[position].equals("E")) {
                    atdButton.getBackground().setColorFilter(0xFFFF6600,
                                    PorterDuff.Mode.MULTIPLY);
            } else if (atdState[position].equals("U")) {
                    atdButton.getBackground().setColorFilter(0xFFFF0000,
                                    PorterDuff.Mode.MULTIPLY);
            } else {
                    atdButton.getBackground().clearColorFilter();
            }
            atdButton.setFocusable(true);
            atdButton.setClickable(true);

            atdButton.setOnClickListener(new OnClickListener() {
                    @Override
                    public void onClick(View view) {
                            Button atdButton = (Button) view
                                            .findViewById(R.id.attendbutton);
                            String test = atdButton.getText().toString();
                            if (test.equals(" ")) {
                                    atdButton.setText("P");
                                    atdState[pos] = "P";
                                    atdButton.getBackground().setColorFilter(0xFF00FF00,
                                                    PorterDuff.Mode.MULTIPLY);
                            } else if (test.equals("P")) {
                                    atdButton.setText("T");
                                    atdState[pos] = "T";
                                    atdButton.getBackground().setColorFilter(0xFFFFFF00,
                                                    PorterDuff.Mode.MULTIPLY);
                            } else if (test.equals("T")) {
                                    atdButton.setText("E");
                                    atdState[pos] = "E";
                                    atdButton.getBackground().setColorFilter(0xFFFF6600,
                                                    PorterDuff.Mode.MULTIPLY);
                            } else if (test.equals("E")) {
                                    atdButton.setText("U");
                                    atdState[pos] = "U";
                                    atdButton.getBackground().setColorFilter(0xFFFF0000,
                                                    PorterDuff.Mode.MULTIPLY);
                            } else if (test.equals("U")) {
                                    atdButton.setText("P");
                                    atdState[pos] = "P";
                                    atdButton.getBackground().setColorFilter(0xFF00FF00,
                                                    PorterDuff.Mode.MULTIPLY);
                            }
                    }
            });
            return (row);
    }

}

我在哪里使用 setText 并为我的按钮着色，你会想要 setChecked 或类似的东西，但希望这会为你指明正确的方向。