在ListView中滚动会丢失文本颜色和字体

Posted 2021-04-21

我不确定它为什么不起作用，但我的代码应该做的很简单。

我有一个ListView，其中包含我在getView（）中声明的默认文本颜色（BLACK）和字体（MONOSPACE），因此在创建视图时一切正常。

当我从列表中选择一个项目时，它应该将文本颜色更改为RED并将字体更改为MONOSPACE和BOLD，如果我单击另一个项目，它会将该项目更改为RED和BOLD并将之前的文本返回到BLACK和NORMAL。这很好用，但如果我滚动远离RED和BOLD文本直到它不可见，然后向后滚动，文本不再是RED和BOLD，而是BLACK和NORMAL。

非常感谢帮助！谢谢

private ArrayList<String> list;
private ListView myView;
private ListAdapter listAdapter;

protected void onCreate(@Nullable Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_list);

    list = new ArrayList<>();
    for (int i = 0; i < 20; i++) {
        list.add("Hello world " + i);
    }
    listAdapter = new ListAdapter();
    myView = (ListView) findViewById(R.id.myList);
    myView.setAdapter(listAdapter);
    myView.setOnItemClickListener(new  AdapterView.OnItemClickListener() {
        @Override
        public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
            TextView tv = (TextView) view.findViewById(R.id.textView);
            tv.setTextColor(Color.RED);
            tv.setTypeface(Typeface.MONOSPACE, Typeface.BOLD);

        }
    });
}

public class ListAdapter extends BaseAdapter {
    @Override
    public View getView(int i, View view, ViewGroup viewGroup) {
        view = getLayoutInflater().inflate(R.layout.listview_layout, null);
        TextView txt = (TextView) view.findViewById(R.id.textView);
        txt.setText(list.get(i));
        txt.setTextColor(Color.BLACK);
        txt.setTypeface(Typeface.MONOSPACE, Typeface.NORMAL);
        return view;
    }
}

答案

好的，首先你要通过标志保持行之间的样式差异。因此，不应将String列表传递给适配器，而应考虑包含字符串和标志对的列表。出现此问题的原因是ListView包含有限的视图数，并且在滚动发生时，它会为它们分配值。

public class MainActivity extends AppCompatActivity {

    private List<Pair> list;
    private ListAdapter listAdapter;
    private ListView myView;
    private int lastClickedPosition = 0;

    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_list);

        list = new ArrayList<>();
        for (int i = 0; i < 20; i++) {
            list.add(new Pair("Hello world " + i, false));
        }
        listAdapter = new ListAdapter();
        myView = (ListView) findViewById(R.id.myList);
        myView.setAdapter(listAdapter);
        myView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                list.get(lastClickedPosition).flag = false;
                list.get(position).flag = true;
                lastClickedPosition = position;
                listAdapter.notifyDataSetChanged();
            }
        });
    }

    public class ListAdapter extends BaseAdapter {
        @Override
        public View getView(int i, View view, ViewGroup viewGroup) {
            view = getLayoutInflater().inflate(R.layout.listview_layout, null);
            TextView txt = (TextView) view.findViewById(R.id.textView);
            txt.setText(list.get(i).text);

            if (list.get(i).flag) {
                txt.setTextColor(Color.RED);
                txt.setTypeface(Typeface.MONOSPACE, Typeface.BOLD);
            } else {
                txt.setTextColor(Color.BLACK);
                txt.setTypeface(Typeface.MONOSPACE, Typeface.NORMAL);
            }

            return view;
        }

        @Override
        public int getCount() {
            return list.size();
        }

        @Override
        public Object getItem(int i) {
            return null;
        }

        @Override
        public long getItemId(int i) {
            return 0;
        }
    }

    static class Pair {
        String text;
        boolean flag;

        Pair(String text, boolean flag){
            this.text = text;
            this.flag = flag;
        }
    }
}