java - 显示循环读取的第一个图像

Question

我想显示用户输入的字母对应的图像。但问题是，循环会重复显示已读取的第一张图像。

public View getView(int position, View convertView, ViewGroup parent) {
    LayoutInflater inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    View rowView = inflater.inflate(R.layout.activity_list, null, true);
    ImageView imageView = (ImageView)rowView.findViewById(R.id.img);

    if (convertView == null) {
        convertView = inflater.inflate(R.layout.activity_list, parent, false);
    }

    for (int loop = 0; loop < ALPHA.length; loop++) {
        for (int j = 0; j < alphaSplit.length; j++) {
            if (alphaSplit[j] == ALPHA[loop]) {
                imageView.setImageResource(ICONS[loop]);
            }
        }
    }
    return rowView;
}

这已经是我修改后的 GET View

public View getView(int position, View convertView, ViewGroup parent) {

    Holder holder;

    if (convertView == null) {
        convertView = inflater.inflate(R.layout.activity_list, null);

        holder = new Holder();
        holder.imageView = (ImageView) convertView.findViewById(R.id.img);

        convertView.setTag(holder);
    } else {
        holder = (Holder) convertView.getTag();
    }

    for (int loop = 0; loop < alphaSplit.length; loop++) {
        for (int j = 0; j < ALPHA.length; j++) {
            if (alphaSplit[loop] == ALPHA[j]) {
                holder.imageView.setImageResource(ICONS[j]);
            }
        }
    }
    return convertView;
}

但它会显示循环获取的最后一个相应图像

Answer 1

你把整个 getView 的想法搞错了。

首先，不要一遍又一遍地定义LayoutInflater。为您的适配器创建一个构造函数，并让它获取 Context 作为参数。

LayoutInflater inflater;
public YourAdapter(Context context) {
    inflater = LayoutInflater.from(context);
}

其次，明智地使用 convertView，将静态容器设置为它的标签:

static class Holder{
    ImageView imageView;
}

public View getView(int position, View convertView, ViewGroup parent) {
    Holder holder;

    if (convertView == null) {
        convertView = inflater.inflate(...); //I'd recommend setting it (*layout, null);

        holder = new Holder();
        holder.imageView = (ImageView) convertView.findViewById(R.id.img);

        convertView.setTag(holder);
    } else {
        holder = (Holder) convertView.getTag();
    }

    for (int loop = 0; loop < ALPHA.length; loop++) {
        for (int j = 0; j < alphaSplit.length; j++) {
            if (alphaSplit[j] == ALPHA[loop]) {
                holder.imageView.setImageResource(ICONS[loop]);
            }
        }
    }

    return convertView;
}

请看，检查 convertView == null 仅用于定义和扩充第一个可见 View 。然后你想更新相同 View 中的数据，这样它就会产生滚动的错觉(而不是每次都实际膨胀新 View )。