在我的应用程序中，我通常有很多异步任务。它们看起来都一样，因此有着相同的设计。所以我想进一步优化一下，并创建一个通用的myasynctask，从中扩展我的asynctasks。但我不知道怎么做。
这是我的一个任务。它们仅在*包围的方法/变量上有所不同：

public class OneOfMyAsyncTasks extends AsyncTask<Void, Void,***Cursor***> {

    private Context                      context;
    private MyProgressDialog             dialog;
    private OnAsyncTaskCompletedListener listener;
    private String                       search;
    private int                          task_id;

    public OneOfMyAsyncTasks(int task_id, Context context, OnAsyncTaskCompletedListener listener) {
        super();

        this.context = context;
        this.listener = listener;
        this.task_id = task_id;
    }

    public OneOfMyAsyncTasks(int task_id, Context context, OnAsyncTaskCompletedListener,
                      ***String search***) {
        super(task_id, context, listener);

      ***this.search = search;***
    }

    protected void attach(Context context, OnAsyncTaskCompletedListener listener) {
        this.context = context;
        this.listener = listener;

        processCreateDialog();
    }

    protected void detach() {
        processDismissDialog();

        if (context != null) {
            context = null;
        }

        if (listener != null) {
            listener = null;
        }
    }

    @Override
    protected***Cursor***doInBackground(Void... voids) {
      ***return MyApplication.getSqliteOpenHelper().fetchSomething(search);***
    }

    @Override
    protected void onPostExecute(***Cursor cursor***) {
        if (listener != null) {
            listener.onAsyncTaskCompleted(task_id,***cursor***);
        }

        detach();
    }

    @Override
    protected void onPreExecute() {
        processCreateDialog();
    }

    private void processCreateDialog() {
        if (context != null) { 
            dialog = MyProgressDialog.show(context, null, null, true, false);
        }
    }

    private void processDismissDialog() {
        if (dialog != null) {
            try {
                dialog.dismiss();
            } catch (Exception exception) {
            }

            dialog = null;
        }
    }
}

我的想法是创建一个myasynctask，它包含上面显示的所有内容，但以下内容除外：
方法做背景
onpostexecute方法
第二个构造器
... 以及asynctask本身的签名（第三个参数）
必须从特定的asynctasks中设置它们，这些asynctasks确实扩展自此泛型myasynctask。
非常感谢您的帮助。
编辑：以下是我到目前为止所做的-没有成功。扩展类抛出以下代码中编写的两个错误。首先是抽象类：

public abstract class MyAsyncTask<A, B, C> extends AsyncTask<A, B, C> {

        protected Context                      context;
        protected MyProgressDialog             dialog;
        protected OnAsyncTaskCompletedListener listener;
        protected int                          task_id;

        public MyAsyncTask(int task_id, Context context, OnAsyncTaskCompletedListener listener) {
            super();

            this.context = context;
            this.listener = listener;
            this.task_id = task_id;
        }

        protected void attach(Context context, OnAsyncTaskCompletedListener listener) {
            this.context = context;
            this.listener = listener;

            processCreateDialog();
        }

        protected void detach() {
            processDismissDialog();

            if (context != null) {
                context = null;
            }

            if (listener != null) {
                listener = null;
            }
        }

        @Override
        protected void onPostExecute(C result) {
            if (listener != null) {
                listener.onAsyncTaskCompleted(task_id, result);
            }

            detach();
        }

        @Override
        protected void onPreExecute() {
            processCreateDialog();
        }

        private void processCreateDialog() {
            if (context != null) {
                dialog = MyProgressDialog.show(context, null, null, true, false);
            }
        }

        private void processDismissDialog() {
            if (dialog != null) {
                try {
                    dialog.dismiss();
                } catch (Exception exception) {
                }

                dialog = null;
            }
        }
    }

下面是一个类扩展这个抽象类的想法。这两个错误写在代码中：

public class MyAsyncTaskImpl extends MyAsyncTask<Void, Void, Cursor> {
    // --> Error: MyAsyncTask cannot be resolved to a type - Create class 'MyAsyncTask<T1, T2, T3>'

    private String search;

    public MyAsyncTaskImpl(int task_id, Context context, OnAsyncTaskCompletedListener listener, String search) {
        super(task_id, context, listener);

        this.search = search;
    }

    @Override
    protected Cursor doInBackground(Void... voids) {
        // --> Error: The method doInBackground(Void...) of type MyAsyncTaskImpl must override or implement a supertype method - Remove '@Override' annotation        

        return MyApplication.getSqliteOpenHelper().fetchSomething(search);
    }
}