Callable 不會從類中返回任何內容

Question

我正在做一個應用程序，它可以抓取網站並獲取一些圖像，效果很好，我創建了一個 ThreadPoolExecutor 和一些可調用對象，但是當我嘗試從我創建的可調用對象中獲取結果時，我無法訪問，它轉到執行異常。

這是刮板類：

public class ImageScraper implements Callable<String>{

Context context = null;
public Logo logoActivity;
Document[] doc = new Document[1];
List<ImageObject> imageList = new ArrayList<ImageObject>();
int pagAnterior;
String url;
int pag;



public ImageScraper(Logo act, String url, int pag, int pagAnterior) {
    this.logoActivity = act;
    this.url = url;
    this.pag = pag;
    this.pagAnterior = pagAnterior;
    context = act.getApplication();

}

@Override
public String call() throws Exception {
    getResponse(url,pag);
    getImages(doc[0]);
    Log.i("listaaa", "listaa  : "+imageList.size());
    String something = "got something";
    return something;
}


public void getImages(Document docfinal)  {

    Log.i("Documento1", "documento1  : "+docfinal);

    Elements entradas = docfinal.select("img[src]");
    Elements titulo = doc[0].select("title");
    String tituloPagina = titulo.text();
    String urlImage = "";

    if(!tituloPagina.toLowerCase().contains("page "+pagAnterior)) {

        for (Element elem : entradas) {

            if (elem.attr("abs:src").toLowerCase().contains("mfiles")) {
                urlImage = elem.attr("abs:src").replace("thumb-", "");
                Log.i("GridVerticalFragment", "Pillando url: " + urlImage);
                ImageObject image = new ImageObject(urlImage);
                Log.i("GridVerticalFragment", "Url Pillada: " + image.getUrl());
                imageList.add(image);
            }

        }
    }
    Log.i("Logo", "Lista2: "+imageList.size());
}


public void getResponse(String urlRoot, int pagina) {
    Log.i("GridVerticalLayaout", "Pagina: "+pagina);
    String url;
    String urlFinal = "";
    if(pagina==0){
        url = urlRoot;
        urlFinal = url;
    }else{
        url = urlRoot.concat("?page="+Integer.toString(pagina));
        urlFinal = url;
    }

    RequestQueue rq = Volley.newRequestQueue(context);
    Log.i("GridVerticalLayaout", "fuuck: "+url);
    Log.i("GridVerticalLayaout", "lool: "+urlFinal);
    StringRequest stringRequest = new StringRequest(Request.Method.GET, urlFinal,
            new Response.Listener<String>() {
                @Override
                public void onResponse(String response) {
                    // Do something with the response
                    doc[0] = Jsoup.parse(response);
                    getImages(doc[0]);

                }
            },
            new Response.ErrorListener() {
                @Override
                public void onErrorResponse(VolleyError error) {
                    // Handle error
                    Log.e("ERROR", "Error occurred ", error);
                }
            });
    rq.add(stringRequest );
}

}

這是主類：

public class Logo extends AppCompatActivity {


public List<ImageObject> GlobalImageList = new ArrayList<ImageObject>() ;
Document[] doc = new Document[1];
String url;
int pagAnterior = 0;
int i = 0;
Context context = null;
public ThreadPoolExecutor executor;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_logo);
    getSupportActionBar().hide();

    Collection<Callable<String>> callableList = new ArrayList<>();

    context = getApplication();

    int NUMBER_OF_CORES = Runtime.getRuntime().availableProcessors();
    executor = new ThreadPoolExecutor(
            NUMBER_OF_CORES*2,
            NUMBER_OF_CORES*2,
            60L,
            TimeUnit.SECONDS,
            new LinkedBlockingQueue<Runnable>()
    );


    while(i<4){
        callableList.add(new ImageScraper(this,"www.google.es,i,i-1););
        i++;
    }

    List<Future<String>> result = null;
    try {
        result = executor.invokeAll(callableList);
    } catch (InterruptedException e) {
        Log.i("Fallo", "Fallo");
        e.printStackTrace();
    }
    for (Future a : result) {
        String SingleImageList = null;

        try {
            SingleImageList = (String) a.get();
            Log.i("Single", "Single"+SingleImageList);
        } catch (InterruptedException e) {
            Log.i("Fallo3", "Fallo3");
            e.printStackTrace();
        } catch (ExecutionException e) {
            Log.i("Fallo2", "Fallo2");
            e.printStackTrace();
        }



}

}


}

這不會返回任何內容，但刮刀完成他的工作，（ getImages() 和 getResponse() 完成工作並更新列表，而不是在 MainClass 的這部分代碼中：

while(i<4){
        callableList.add(new ImageScraper(this,"www.google.es,i,i-1););
        i++;
    }

如果我為此更改它（該類不稱為在類中創建的可調用對象），它會起作用，返回字符串：

        while(i<4){
        callableList.add(new Callable<String>() {
            public String call() throws Exception {
                return "haha";
            }
        });
        i++;
    }

有人可以幫我解決這個問題嗎？ 我已經閱讀了很多，根據我所閱讀的內容，我在Scraper類中的內容很好，但我仍然不明白。

對不起，英語不好，我正在嘗試:)，我不想返回一個字符串我想返回一個 ArrayList，我在代碼中返回一個字符串，因為認為這是返回 ArrayList 的問題，但似乎是這樣是不是，再次，謝謝！

Answer 1

請檢查這行代碼

while(i<4){
    callableList.add(new ImageScraper(this,"www.google.es,i,i-1););
    i++;
}    

你沒有關閉雙引號！ 相反，試試這個代碼

while(i<4){
    callableList.add(new ImageScraper(this,"www.google.es",i,i-1););
    i++;
}