Android 我应该在异步任务中将片段作为弱引用传递吗？

Posted 2023-05-07

【中文标题】Android 我应该在异步任务中将片段作为弱引用传递吗？

【英文标题】：Android should I pass fragment as weak reference in async task?

【发布时间】：2020-12-10 16:20:39

【问题描述】：

我有以下加载大量数据的片段，这个片段有一个内部静态类，它以以下方式扩展 AsyncTask 并弱引用片段本身to prevent memory leaks：

public class PokemonDescriptionFragment extends Fragment 

////////Code

   private static class LoadPokemonData extends AsyncTask<Void, Void, Pokemon> 

    private WeakReference<PokemonDescriptionFragment> appReference;//FIXME Should I pass fragment as weak reference?

    LoadPokemonData(PokemonDescriptionFragment context) 
        appReference = new WeakReference<>(context);
    

    /**
     * Executed before starting the BACKGROUND THREAD
     * Executed in the MAIN THREAD
     */
    @Override
    protected void onPreExecute() 
        final PokemonDescriptionFragment fragment = appReference.get();
        if (fragment == null) return;
        GenericUtils.changeVisibility(View.VISIBLE, fragment.pokedexDataProgressBar, fragment.biologyProgressBar, fragment.statsDataProgressBar, fragment.abilitiesProgressBar, fragment.etymologyProgressBar);
        GenericUtils.changeVisibility(View.GONE, fragment.llPokedexContainer);
    

    /**
     * Executes after onPreExecute.
     * Is executed in the BACKGROUND THREAD
     * Here you can call "publishProgress" method that executes the "onProgressUpdate" method in Main thread ,
     * however , in this case , as I use indeterminated progress bar isn't necessary
     *
     * @return its sends the values to "onPostExecute"
     */
    @Override
    protected Pokemon doInBackground(Void... params) 
        final PokemonDescriptionFragment fragment = appReference.get();
        if (fragment == null) return null;
        fragment.initializePokemonData();
        return fragment.selectedPokemon;
    

    /**
     * Executes after doInBackground
     * Executed in the MAIN THREAD
     */
    @Override
    protected void onPostExecute(Pokemon pokemon) 

        final PokemonDescriptionFragment fragment = appReference.get();
        if (fragment == null) return;
        if (Objects.nonNull(pokemon)) 
            MainActivity.setSelectedPokemon(pokemon);
            fragment.abilityAdapter.refreshAbilities(fragment.abilityList);
        
        GenericUtils.changeVisibility(View.GONE, fragment.pokedexDataProgressBar, fragment.biologyProgressBar, fragment.statsDataProgressBar, fragment.abilitiesProgressBar, fragment.etymologyProgressBar);
        GenericUtils.changeVisibility(View.VISIBLE, fragment.llPokedexContainer);
        fragment.displayFullData();
    

但是，我不确定这是否 100% 安全，我将片段作为弱引用传递，因为我需要访问片段具有的一些方法和属性。此外，如果您检查我的代码，我声明了 3 次：

  final PokemonDescriptionFragment fragment = appReference.get();
    if (fragment == null) return null;

在异步任务中，而不是将其声明为异步任务的全局属性并在3种方法中引用它，这是正确的吗？如果我将它添加为 Asny 任务的全局属性有什么问题吗？

【参考方案1】：

在AsyncTask 中添加Fragment 作为WeakReference 是安全的，不应该成为内存泄漏问题。

另外，最好取消片段中的AsyncTask onDestroy()，以免浪费资源。

但请考虑完全重构您的代码，以获得更好的architecture，从而完全避免在 AsyncTask 中需要 Fragment 上下文。