Question

我正在尝试使用AsyncTask将对象添加到我的SQLite数据库中。我有4个类：MainActivity，DBHelper，ToDo_Item和名为DatabaseAsyncAdd的AsyncTask内部类

class ToDo_Item {

//MEMBER ATTRIBUTES
private int _id;
private String description;
private int is_done;

public ToDo_Item() {
}

public ToDo_Item(String desc, int done) {
    description = desc;
    is_done = done;
}

public int getId() {
    return _id;
}
public void setId(int id) {
    _id = id;
}

public String getDescription () {
    return description;
}
public void setDescription (String desc) {
    description = desc;
}

public int getIs_done() {
    return is_done;
}

public void setIs_done(int done) {
    is_done = done;
}

}

以下是我尝试使用的DBHelper的方法：

public void addToDoItem(ToDo_Item task) {
    SQLiteDatabase db = this.getWritableDatabase();
    ContentValues values = new ContentValues();

    //ADD KEY-VALUE PAIR INFORMATION FOR THE TASK DESCRIPTION
    values.put(KEY_DESCRIPTION, task.getDescription()); // task name

    //ADD KEY-VALUE PAIR INFORMATION FOR
    //IS_DONE VALUE: 0- NOT DONE, 1 - IS DONE
    values.put(KEY_IS_DONE, task.getIs_done());

    // INSERT THE ROW IN THE TABLE
    db.insert(DATABASE_TABLE, null, values);
    taskCount++;

    // CLOSE THE DATABASE CONNECTION
    db.close();
}

我的主要包括AsyncTask

public class MainActivity extends Activity {

protected DBHelper mDBHelper;
private List<ToDo_Item> list;
private MyAdapter adapt;
private EditText myTask;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    // TASK 1: LAUNCH THE LAYOUT REPRESENTING THE MAIN ACTIVITY
    setContentView(R.layout.activity_main);

    // TASK 2: ESTABLISH REFERENCES TO THE UI
    //      ELEMENTS LOCATED ON THE LAYOUT
    myTask = (EditText) findViewById(R.id.editText1);

    // TASK 3: SET UP THE DATABASE
    mDBHelper = new DBHelper(this);
    /*
    list = mDBHelper.getAllTasks();
    adapt = new MyAdapter(this, R.layout.todo_item, list);
    ListView listTask = (ListView) findViewById(R.id.listView1);
    listTask.setAdapter(adapt);
    */
}

@Override
protected void onResume(){
    super.onResume();
    list = mDBHelper.getAllTasks();
    adapt = new MyAdapter(this, R.layout.todo_item, list);
    ListView listTask = (ListView) findViewById(R.id.listView1);
    listTask.setAdapter(adapt);
}

//BUTTON CLICK EVENT FOR ADDING A TODO TASK
public void addTaskNow(View view) {
    String s = myTask.getText().toString();
    if (s.isEmpty()) {
        Toast.makeText(getApplicationContext(), "A TODO task must be entered.", Toast.LENGTH_SHORT).show();
    } else {

        //BUILD A NEW TASK ITEM AND ADD IT TO THE DATABASE
        ToDo_Item task = new ToDo_Item(s, 0);
        mDBHelper.addToDoItem(task);
        new DatabaseAsyncAdd().execute(task);

        // CLEAR OUT THE TASK EDITVIEW
        myTask.setText("");

        // ADD THE TASK AND SET A NOTIFICATION OF CHANGES
        adapt.add(task);
        adapt.notifyDataSetChanged();
    }
}

//BUTTON CLICK EVENT FOR DELETING ALL TODO TASKS
public void clearTasks(View view) {
    mDBHelper.clearAll(list);
    adapt.notifyDataSetChanged();
}

private class DatabaseAsyncAdd extends AsyncTask<ToDo_Item, String, Void> {
    int progress_status;

    @Override
    protected void onPreExecute() {
        // UPDATE THE UI IMMEDIATELY BEFORE BACKGROUND WORK IS PERFORMED
        super.onPreExecute();
        Toast.makeText(MainActivity.this, "Accessing Database",
                Toast.LENGTH_SHORT).show();

    }

    @Override
    protected Void doInBackground(ToDo_Item... task) {
        String s = myTask.getText().toString();
        mDBHelper.addToDoItem(task);
        return null;
    }


    @Override
    protected void onPostExecute(Void result) {
        super.onPostExecute(result);

    }
}

//******************* ADAPTER ******************************
private class MyAdapter extends ArrayAdapter<ToDo_Item> {
    Context context;
    List<ToDo_Item> taskList = new ArrayList<ToDo_Item>();

    public MyAdapter(Context c, int rId, List<ToDo_Item> objects) {
        super(c, rId, objects);
        taskList = objects;
        context = c;
    }

//******************* TODO TASK ITEM VIEW ******************************
    /**
     * THIS METHOD DEFINES THE TODO ITEM THAT WILL BE PLACED
     * INSIDE THE LIST VIEW.
     *
     * THE CHECKBOX STATE IS THE IS_DONE STATUS OF THE TODO TASK
     * AND THE CHECKBOX TEXT IS THE TODO_ITEM TASK DESCRIPTION.
     */

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        CheckBox isDoneChBx = null;
        if (convertView == null) {
            LayoutInflater inflater = (LayoutInflater) context
                    .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            convertView = inflater.inflate(R.layout.todo_item, parent, false);
            isDoneChBx = (CheckBox) convertView.findViewById(R.id.chkStatus);
            convertView.setTag(isDoneChBx);
            isDoneChBx.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View view) {
                    CheckBox cb = (CheckBox) view;
                    ToDo_Item changeTask = (ToDo_Item) cb.getTag();
                    changeTask.setIs_done(cb.isChecked() == true ? 1 : 0);
                    mDBHelper.updateTask(changeTask);
                }
            });
        } else {
            isDoneChBx = (CheckBox) convertView.getTag();
        }
        ToDo_Item current = taskList.get(position);
        isDoneChBx.setText(current.getDescription());
        isDoneChBx.setChecked(current.getIs_done() == 1 ? true : false);
        isDoneChBx.setTag(current);
        return convertView;
    }
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu.
    getMenuInflater().inflate(R.menu.menu_main, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    int id = item.getItemId();

    //noinspection SimplifiableIfStatement
    if (id == R.id.action_settings) {
        return true;
    }

    return super.onOptionsItemSelected(item);
}
}

我正在尝试在addtasknow方法上创建一个ToDo_Item，这是一个按钮单击方法。然后将该对象传递给DatabaseASyncAdd中的execute方法。 mDBHelper.addToDoItem（task）说＆＃34; ToDo_Item不能应用于ToDo_Item []＆＃34;虽然它在AsyncTask类之外工作。我没有正确地调用执行吗？

Answer 1

将mDBHelper.addToDoItem(task)更改为mDBHelper.addToDoItem(task[0])

private class DatabaseAsyncAdd extends AsyncTask<ToDo_Item, String, Void> {
    int progress_status;

    @Override
    protected void onPreExecute() {
        // UPDATE THE UI IMMEDIATELY BEFORE BACKGROUND WORK IS PERFORMED
        super.onPreExecute();
        Toast.makeText(MainActivity.this, "Accessing Database",
                Toast.LENGTH_SHORT).show();

    }

    @Override
    protected Void doInBackground(ToDo_Item... task) {
        //String s = myTask.getText().toString();
        mDBHelper.addToDoItem(task[0]);
        return null;
    }


    @Override
    protected void onPostExecute(Void result) {
        super.onPostExecute(result);

    }
}

Answer 2

在

mDBHelper.addToDoItem(task);

task是ToDo_Item[]。这就是ToDo_Item...在签名中的含义。它被称为varargs，用于“变量参数”。

将对象传递给AsyncTask方法不能应用于给定类型

2 个答案: