android - 如何在 gridView 中更快地加载应用程序的图像(图标)？

Question

我正在显示安装在 gridView 中的所有应用程序。当加载大量应用程序时，比方说 30 个或更多，图标将显示在默认的 Android 图标上，然后几秒钟后更新为正确的图标。我想知道我可以对我的代码进行改进以使图标图像显示更快。

加载以下内容:new LoadIconsTask().execute(mApps.toArray(new AppsInstalled[]{}));

这是我的工作。

private class LoadIconsTask extends AsyncTask<AppsInstalled, Void, Void>{

        @Override
        protected Void doInBackground(AppsInstalled... params) {
            // TODO Auto-generated method stub
            Map<String, Drawable> icons = new HashMap<String, Drawable>();
            PackageManager manager = getApplicationContext().getPackageManager();

            // match package name with icon, set Adapter with loaded Map
            for (AppsInstalled app : params) {
                String pkgName = app.getAppUniqueId();
                Drawable ico = null;
                try {
                    Intent i = manager.getLaunchIntentForPackage(pkgName);
                    if (i != null) {
                        ico = manager.getActivityIcon(i);
                    }               
                } catch (NameNotFoundException e) {
                    Log.e(TAG, "Unable to find icon match based on package: " + pkgName 
                            + " : " + e.getMessage());
                }
                icons.put(app.getAppUniqueId(), ico);
            }
            mAdapter.setIcons(icons);
            return null;
        }

在我使用 loadIconsTask() 之前填充我的应用程序列表

private List<App> loadInstalledApps(boolean includeSysApps) {
    List<App> apps = new ArrayList<App>();

    // the package manager contains the information about all installed apps
    PackageManager packageManager = getPackageManager();

    List<PackageInfo> packs = packageManager.getInstalledPackages(0); // PackageManager.GET_META_DATA

    for (int i = 0; i < packs.size(); i++) {
        PackageInfo p = packs.get(i);
        ApplicationInfo a = p.applicationInfo;
        // skip system apps if they shall not be included
        if ((!includeSysApps)
                && ((a.flags & ApplicationInfo.FLAG_SYSTEM) == 1)) {
            continue;
        }
        App app = new App();
        app.setTitle(p.applicationInfo.loadLabel(packageManager).toString());
        app.setPackageName(p.packageName);
        app.setVersionName(p.versionName);
        app.setVersionCode(p.versionCode);
        CharSequence description = p.applicationInfo
                .loadDescription(packageManager);
        app.setDescription(description != null ? description.toString()
                : "");
        apps.add(app);
    }
    return apps;
}

关于我的适配器类，它是标准的。我的 getView() 如下所示:

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

        AppViewHolder holder;
        if (convertView == null) {
            convertView = mInflater.inflate(R.layout.row, null);

            // creates a ViewHolder and stores a reference to the children view
            // we want to bind data to
            holder = new AppViewHolder();
            holder.mTitle = (TextView) convertView.findViewById(R.id.apptitle);
            holder.mIcon = (ImageView) convertView.findViewById(R.id.appicon);
            convertView.setTag(holder);
        } else {
            // reuse/overwrite the view passed assuming that it is castable!
            holder = (AppViewHolder) convertView.getTag();
        }

        App app = mApps.get(position);

        holder.setTitle(app.getTitle());
        if (mIcons == null || mIcons.get(app.getPackageName()) == null) {
            holder.setIcon(mStdImg);
        } else {
            holder.setIcon(mIcons.get(app.getPackageName()));
        }

        return convertView;
    }

有没有更好的方法？我能否以某种方式将图标的图像存储在数据结构中，并且当我返回此 Activity 时可以跳过 loadIconsTask？那可能吗？提前谢谢你。

Answer 1

您可以使用 Picasso带有自定义 RequestHandler 的库以在后台加载图标。

1. 首先创建一个 RequestHandler，它将处理需要加载应用程序图标的特定情况。

   public class AppIconRequestHandler extends RequestHandler {
   
       /** Uri scheme for app icons */
       public static final String SCHEME_APP_ICON = "app-icon";
   
       private PackageManager mPackageManager;
   
       public AppIconRequestHandler(Context context) {
           mPackageManager = context.getPackageManager();
       }
   
       /**
        * Create an Uri that can be handled by this RequestHandler based on the package name
        */
       public static Uri getUri(String packageName) {
           return Uri.fromParts(SCHEME_APP_ICON, packageName, null);
       }
   
       @Override
       public boolean canHandleRequest(Request data) {
           // only handle Uris matching our scheme
           return (SCHEME_APP_ICON.equals(data.uri.getScheme()));
       }
   
       @Override
       public Result load(Request request, int networkPolicy) throws IOException {
           String packageName = request.uri.getSchemeSpecificPart();
           Drawable drawable;
           try {
               drawable = mPackageManager.getApplicationIcon(packageName);
           } catch (PackageManager.NameNotFoundException ignored) {
               return null;
           }
   
           Bitmap bitmap = ((BitmapDrawable) drawable).getBitmap();
           return new Result(bitmap, Picasso.LoadedFrom.DISK);
       }
   }
   

2. 在您的适配器中，创建一个 Picasso 实例并添加您的 RequestHandler。

   // field variable
   private Picasso mPicasso;
   
   // in constructor
   Picasso.Builder builder = new Picasso.Builder(context);
   builder.addRequestHandler(new AppIconRequestHandler(context));
   mPicasso = builder.build();
   

3. 在您的适配器的 getView() 中使用 Picasso 加载图标。

   mPicasso.load(AppIconRequestHandler.getUri(app.packageName)).into(holder.mIcon);