bindView switch-case 性能问题

Question

我目前正在编写一个应用程序，该应用程序需要在 ListView 中设置图像，具体取决于我的数据库中的条目。

我通过我的customCursorAdapter 的bindView() 方法直接通过一个switch-case 实现了这一点。由于bindView 经常被调用，我的ListView 开始结结巴巴，一切都变慢了。有没有办法“外包”这个数据库比较？这是我的源代码：

public class customCursorAdapter extends CursorAdapter {
    public customCursorAdapter(Context context, Cursor cursor){
        super(context, cursor, 0);
    }

    @Override
    public View newView(Context context, Cursor cursor, ViewGroup parent) {
        return LayoutInflater.from(context).inflate(R.layout.layout_listitems, parent, false);
    }

    @Override
    public void bindView(View view, Context context, Cursor cursor) {

        // Find fields to populate in inflated template
        TextView brand = (TextView) view.findViewById(R.id.listBrand);
        TextView model = (TextView) view.findViewById(R.id.listModel);
        TextView lastMoved = (TextView) view.findViewById(R.id.dateContent);
        TextView lastCharged = (TextView) view.findViewById(R.id.lastChargedContent);
        ImageView brandPhoto = (ImageView) view.findViewById(R.id.brandImage);
        // Extract properties from cursor
        String brandList = cursor.getString(cursor.getColumnIndexOrThrow("Brand"));
        String modelList = cursor.getString(cursor.getColumnIndexOrThrow("Model"));
        String lastMovedList = cursor.getString(cursor.getColumnIndexOrThrow("LastMoved"));
        String lastChargedList = cursor.getString(cursor.getColumnIndexOrThrow("LastCharge"));

            switch(brandList){
                case "Ferrari":
                    brandPhoto.setImageResource(R.drawable.ferrari);
                    break;
                case "Porsche":
                    brandPhoto.setImageResource(R.drawable.porsche);
                    break;
                case "VW":
                case "Volkswagen":
                    brandPhoto.setImageResource(R.drawable.volkswagen);
                    break;
                case "Mini":
                    brandPhoto.setImageResource(R.drawable.mini);
                    break;
                case "Audi":
                    brandPhoto.setImageResource(R.drawable.audi);
                    break;
                case "Aston Martin":
                    brandPhoto.setImageResource(R.drawable.aston);
                    break;
                case "Alpina":
                    brandPhoto.setImageResource(R.drawable.alpina);
                    break;
                case "Jeep":
                    brandPhoto.setImageResource(R.drawable.jeep);
                    break;
                case "Bentley":
                    brandPhoto.setImageResource(R.drawable.bentley);
                    break;
                case "Dodge":
                    brandPhoto.setImageResource(R.drawable.dodge);
                    break;
                case "Fiat":
                    brandPhoto.setImageResource(R.drawable.fiat);
                    break;
                case "Ford":
                    brandPhoto.setImageResource(R.drawable.ford);
                    break;
                case "Lexus":
                    brandPhoto.setImageResource(R.drawable.lexus);
                    break;
                case "Mercedes":
                    brandPhoto.setImageResource(R.drawable.mercedes);
                    break;
                case "Maybach":
                    brandPhoto.setImageResource(R.drawable.maybach);
                    break;
                case "Peugeot":
                    brandPhoto.setImageResource(R.drawable.peugeot);
                    break;
                case "Skoda":
                case "Škoda":
                    brandPhoto.setImageResource(R.drawable.skoda);
                    break;
                case "Rolls Royce":
                    brandPhoto.setImageResource(R.drawable.rolls);
                    break;
                case "Smart":
                    brandPhoto.setImageResource(R.drawable.smart);
                    break;
                case "Opel":
                    brandPhoto.setImageResource(R.drawable.opel);
                    break;
                case "Nissan":
                    brandPhoto.setImageResource(R.drawable.nissan);
                    break;
                case "Alfa Romeo":
                    brandPhoto.setImageResource(R.drawable.alfa);
                    break;
                case "BMW":
                    brandPhoto.setImageResource(R.drawable.bmw);
                    break;
                case "Seat":
                    brandPhoto.setImageResource(R.drawable.seat);
                    break;
                case "Lamborghini":
                    brandPhoto.setImageResource(R.drawable.lamborghini);
                    break;
                default: brandPhoto.setImageResource(R.drawable.ic_directions_carhd);
            }

        // Populate fields with extracted properties
        brand.setText(brandList);
        model.setText(modelList);
        lastMoved.setText(lastMovedList);
        lastCharged.setText(lastChargedList);
    }
}

Answer 1

我可以从您的代码中看到，品牌和与之关联的图像之间存在一对一的映射关系。我不知道您为什么不将资源的 id 放入数据库中，这样您就不必在 brandList 案例中传递 brandList 并在每次必须在每个您的每个中填充图像时进行比较项目清单。

因此，我强烈建议将图像名称保存在您从中获取其他信息的同一数据库表中。这样您只需获取与品牌关联的图像名称，然后将其作为图像资源放入您的ImageView。

因此，您需要执行以下操作。首先准备一个 HashMap 包含图像的资源 ID。

String[] images = {"ferrari", "alpina", "porsche", "volkswagen", .......};
Map<String, Integer> brandImagesMap = new HashMap<String, Integer>();

for(String imageName : images) {
    int drawableResourceId = this.getResources().getIdentifier(imageName, "drawable", this.getPackageName());
    brandImagesMap.put(imageName, drawableResourceId);
}

一旦您的地图在customCursorAdapter 类的构造函数中填充了图像的资源ID，您就可以轻松地从地图中高效地获取图像资源ID，并将其作为ImageView 的资源。请注意，我假设您将图像的名称保留在数据库表的单独列中。

String photoResourceName = cursor.getString(cursor.getColumnIndexOrThrow("Photo"));
brandPhoto.setImageResource(brandImagesMap.get(photoResourceName));

代码未经测试。请根据您的要求进行修改。

更新

使用 Glide 在您的 RecyclerView 中加载图像。它的实现非常简单，当然也很高效。

在您的bindView 函数中，只需将加载图像的代码替换为以下代码。

Glide.with(context)
    .load(brandImagesMap.get(photoCol))
    .fitCenter()
    .placeholder(R.drawable.ic_directions_carhd)
    .into(myHolder.brandPhoto);

如需了解更多 Glide 使用方法，请关注this link。