android - ListView 很慢-android

Question

我想在我的 ListView 中显示资源目录中的图像(所有图像都以 png 格式保存)，但它非常慢。我是一个完全的菜鸟，所以我需要有关异步任务的帮助以消除延迟。

列表适配器:

   public class MyListAdapter extends ArrayAdapter < SettingsItem > {

     Context context;
     List < SettingsItem > items;
     public MyListAdapter(Context context, int resource, List < SettingsItem > objects) {
       super(context, resource, objects);
       this.context = context;
       items = objects;
     }

     @Override
     public View getView(int position, View itemView, ViewGroup parent) {

       ViewHolder holder;
       if (itemView == null) {
         LayoutInflater inflater = ((Activity) context).getLayoutInflater();
         itemView = inflater.inflate(R.layout.settings_items, parent, false);

         holder = new ViewHolder();
         holder.imageView = (ImageView) itemView.findViewById(R.id.item_icon);
         holder.textView = (TextView) itemView.findViewById(R.id.item_text);

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

       SettingsItem settingsItem = items.get(position);

       if (settingsItem != null) {
         holder.textView.setText(settingsItem.getName());
         new ImageDownloaderTask(holder.imageView, getContext(), settingsItem.getIcon_id()).execute();
       }
       return itemView;
     }
     static class ViewHolder {
       ImageView imageView;
       TextView textView;
     }
   }

行类:

public class SettingsItem{
    private String name;
    private int icon_id;
    public SettingsItem(String a, int b){

        super();
        name=a;
        icon_id=b;
    }

    public String getName() {
        return name;
    }

    public int getIcon_id() {
        return icon_id;
    }
}

异步任务:

class ImageDownloaderTask extends AsyncTask<String, Void, Bitmap> {
    private final WeakReference<ImageView> imageViewReference;
    Context context;
    int id;
    public ImageDownloaderTask(ImageView imageView, Context context, int id) {
        imageViewReference = new WeakReference<ImageView>(imageView);
        this.context=context;
        this.id=id;
    }

    @Override
    protected Bitmap doInBackground(String... params) {
        return BitmapFactory.decodeResource(context.getResources(),id );
    }

    @Override
    protected void onPostExecute(Bitmap bitmap) {
        if (isCancelled()) {
            bitmap = null;
        }

        if (imageViewReference != null) {
            ImageView imageView = imageViewReference.get();
            if (imageView != null) {
                if (bitmap != null) {
                    imageView.setImageBitmap(bitmap);
                } else {
                    imageView.setImageResource(R.drawable.medical_bag);
                }
            }
        }
    }
}

我真的需要一些帮助。
提前致谢。 :)

Answer 1

我建议您使用 Glide库，这将为您的应用程序中的图像加载带来性能，并且非常易于使用。它还支持获取、解码和显示视频静止图像、图像和动画 GIF。

它使滚动任何类型的图像列表尽可能流畅和快速，但 Glide 对于几乎任何需要获取、调整大小和显示远程图像的情况也是有效的。

Glide is a fast and efficient open source media management and image loading framework for Android that wraps media decoding, memory and disk caching, and resource pooling into a simple and easy to use interface.

将 Glide 添加到您的项目中:

dependencies {
    compile 'com.github.bumptech.glide:glide:3.6.0'
    compile 'com.android.support:support-v4:19.1.0'
}

官方页面的listview用法如下:

@Override
public View getView(int position, View recycled, ViewGroup container) {
    final ImageView myImageView;
    if (recycled == null) {
        myImageView = (ImageView) inflater.inflate(R.layout.my_image_view,
                container, false);
    } else {
        myImageView = (ImageView) recycled;
    }

    String url = myUrls.get(position);

    Glide.with(myFragment)
        .load(url)
        .centerCrop()
        .placeholder(R.drawable.loading_spinner)
        .crossFade()
        .into(myImageView);

    return myImageView;
}

作为引用，另一个项目使用这个库来实现更快的图像加载和更好的滚动:https://github.com/chrisbanes/cheesesquare