ViewHolder 模式 - 如何正确更新视图

Question

在扩展的 ArrayAdapter 中实现 viewHolder 模式，并在线性布局中实现 onClickListener 时，此 LinearLayout 的背景颜色发生了变化但对于其他随机行也是如此！

这是我的代码（已删除 viewHolder 以仅包含错误）：

public class CustomFeedsAdapter extends ArrayAdapter<CustomCommunityQuestion>{

    private static final String TAG = "CustomFeedsAdapter";
    private Context context;
    private ArrayList<CustomCommunityQuestion> customCommunityQuestions;

    public CustomFeedsAdapter(Context context, ArrayList<CustomCommunityQuestion> customCommunityQuestions) {
        super(context, -1, customCommunityQuestions);
        this.context = context;
        this.customCommunityQuestions = customCommunityQuestions;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        View rowView = convertView;

        // reuse views
        final ViewHolder holder;
        if (convertView == null) {
            holder = new ViewHolder();
            LayoutInflater inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            rowView = inflater.inflate(R.layout.cards_feeds_row, null, false);
            holder.buttonFollow = (LinearLayout) rowView.findViewById(R.id.follow_layout);

            rowView.setTag(holder);
        } else {
            holder = (ViewHolder) rowView.getTag();
        }

        final CustomCommunityQuestion currentQuestion = customCommunityQuestions.get(position);

        // Set onClick Listeners
        holder.buttonFollow.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                VolleySingleton volleySingleton = VolleySingleton.getInstance(context);
                StringRequest followJsonObjectRequest = new StringRequest(Request.Method.GET,
                        "http://private-e9644-popxoandroid.apiary-mock.com/quest_follow/1/0",
                        new Response.Listener<String>() {
                            @Override
                            public void onResponse(String response) {
                                try {
                                    Log.d(TAG, response);
                                    JSONObject responseObject = new JSONObject(response);
                                    String message = responseObject.getString("message");
                                    Integer success = responseObject.getInt("success");
                                    Toast.makeText(context,message,Toast.LENGTH_SHORT).show();
                                    if(success!=0){
                                        holder.buttonFollow.setBackgroundColor(R.color.holo_blue_bright); // Here the button I wish to update doesn't get the color, but instead some weird random row's button get's changed.
                                        holder.buttonFollow.setEnabled(false);
                                    }
                                } catch (Exception e) {
                                    e.printStackTrace();
                                }
                            }
                        },
                        new Response.ErrorListener() {

                            @Override
                            public void onErrorResponse(VolleyError error) {
                                Toast.makeText(context, "There was some error! You were unable to follow", Toast.LENGTH_SHORT).show();
                                error.printStackTrace();
                                Log.e(TAG,error.getMessage());
                            }
                        });
                volleySingleton.addToRequestQueue(followJsonObjectRequest);
            }
        });

        return rowView;
    }

    private class ViewHolder {
        private LinearLayout buttonFollow;
     }
}

Answer 1

问题是列表项的回收：

@Override
public View getView(int position, View convertView, ViewGroup parent) {
    View rowView = convertView;

    // reuse views
    final ViewHolder holder;
    if (convertView == null) {
        ...
    } else {
        holder = (ViewHolder) rowView.getTag();
        //!!!
        // here the view item is recycled but
        // holder.buttonFollow is not reset to its initial state
    }

解决方案：您的 CustomFeedsAdapter 必须记住每个项目的成功统计数据

Answer 2

你在做什么

假设当前可见的行位于位置 0、1、2。您正在更新一个特定的 ViewHolder，它已被设置为特定的标签（使用更好的词）- 视图。稍后调用 holder = (ViewHolder)rowview.getTag() 时会重新使用此视图。为了便于说明，我们假设您正在更新位置 1 的视图。

滚动 listView 时会发生什么

当您滚动列表视图时，旧视图会通过从标签中获取持有者来重新使用。这意味着您之前更改的视图现在正在重新使用。

你需要做什么来代替

所以当你需要更新你的视图时，首先更新一个相关的变量。例如：

在您的 CustomCommunityQuestion class 中创建一个属性并实现 getter 和 setter，如下所示：

boolean isBlue;

public void setIsBlue(booelan isblue){
     this.isBlue = isblue;
}

public boolean isBlue(){
    return isBlue;
}

现在在您的按钮 onClickListener 中，您可以将变量 isBlue 设置为 yes，然后调用 notifyDataSetChanged()。此外，像这样处理属性 isBlue：

只需检查 isBlue 状态并相应地设置颜色

if(customCommunityQuestions.get(position).isBlue()){
       holder.buttonFollow.setBackgroundColor(R.color.holo_blue_bright);
}else{
     holder.buttonFollow.setBackgroundColor(R.color.black);
}

希望对您有所帮助！

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