Question

我有一个 ArrayList<Integer>

我希望将其传递给 AsyncTask<ArrayList<Integer>, void, void>。但在 doInBackground(ArrayList<Integer>...params)函数，我无法接收我传递的arrayList。

在doInBackground内，我使用ArrayList<Integer> arr = params[0]，然后log(arr.size()) is 0 我的代码：

class count  extends AsyncTask<Void, Integer, ArrayList<Integer>>{

    ArrayList<Integer> arr = new ArrayList<Integer>();
    ArrayList<Integer> temp = new ArrayList<Integer>();
    @SuppressWarnings("unchecked")
    @Override
    protected ArrayList<Integer> doInBackground(Void... params) {
        // TODO Auto-generated method stub
        for(int i = 1; i <= 100; i++){
            SystemClock.sleep(200);
            arr.add(i);
            if(i % 10 == 0){
                temp = arr;
                //Log.d("DEBUG", "Length of temp = "+ temp.size());
                arr.clear();
                mean task1 = new mean();
                task1.execute(temp);
            }
            publishProgress(i);
        }
        return arr;
    }
    @Override
    protected void onProgressUpdate(Integer... values) {
        // TODO Auto-generated method stub
        super.onProgressUpdate(values);
        tvNum.setText(values[0]+"");
    }

}

class mean extends AsyncTask<ArrayList<Integer>, Integer, ArrayList<Integer>>{

    @Override
    protected ArrayList<Integer> doInBackground(
            ArrayList<Integer>... params) {
        // TODO Auto-generated method stub
        ArrayList<Integer> arrL =new ArrayList<Integer>();
        arrL= params[0];
        Log.d("DEBUG","iNPUT Size = " + arrL.size());
        return null;
    }

}

请帮帮我，感谢。

Answer 1

简单的例子供您理解。比如

public class MainActivity extends Activity {
    List<CalcPrimesTask> taskList;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        taskList = new ArrayList<CalcPrimesTask>();
    }

    public void onClickStart(View view) {
        EditText maximumEditText = (EditText) findViewById(R.id.maximumEditText);
        int maxNum = Integer.parseInt(maximumEditText.getText().toString());
        CalcPrimesTask task = new CalcPrimesTask(this);
        taskList.add(task);
        task.execute(maxNum);
        Toast.makeText(getApplicationContext(), "New run queued.", Toast.LENGTH_SHORT).show();
    }

    public void onStopClick(View view) {
        for (CalcPrimesTask task : taskList) {
            task.cancel(true);
        }
        Toast.makeText(getApplicationContext(), "All runs cancelled.", Toast.LENGTH_SHORT).show();
    }
}

和

public class CalcPrimesTask extends AsyncTask<Integer, String, List<Integer>> {

    Activity activity;

    public CalcPrimesTask(Activity mainActivity) {
        activity = mainActivity;
    }

    @Override
    protected List<Integer> doInBackground(Integer... params) {
        int maxNum = params[0];
        List<Integer> primeList = new ArrayList<Integer>();
        for (int i = 2; i <= maxNum ; i++) {
            int maxCalc = (int)Math.sqrt(i);
            boolean isPrime = true;
            for (int j = 2; j <= maxCalc ; j++) {
                if (i % j == 0) {
                    isPrime = false;
                    break;
                }
            }
            if (isPrime) {
                primeList.add(i);
                publishProgress("Prime " + i + " found.");
                try {
                    Thread.sleep(1000);
                } catch (InterruptedException e) {
                }
            }
        }
        return primeList;
    }

    @Override
    protected void onProgressUpdate(String... values) {
        TextView messageView = (TextView) activity.findViewById(R.id.messageText);
        messageView.setText(values[0]);
        super.onProgressUpdate(values);
    }

    @Override
    protected void onPostExecute(List<Integer> result) {
        TextView messageView = (TextView) activity.findViewById(R.id.messageText);
        messageView.setText("Total of " + result.size() + " primes found.");
        super.onPostExecute(result);
    }
}

如果您的手可用时间，请阅读Android AsyncTask。运气最好！

Answer 2

如果在调用execute（）时将Arraylist作为唯一参数传递，则它应该在params [0]中。例如，

   YourTask.execute(YourList);

你可以在ASyncTask里面访问它：

Arraylist<Integer> myList = params[0];

Android中的AsyncTask（传递ArrayList <integer>）</integer>

2 个答案: