java - Android - 删除了 ArrayList 中的多个对象，但适配器无法正确更新

Question

我有一个对象的 ArrayList，用作 ListView 的一行。我有一种方法，可以在长按 ListView 中删除并相应更新选中的项目。但是，当该应用程序运行时，所发生的只是那些选中的项目现在变为未选中状态——该项目根本没有被删除。

这是我的 onClick 代码。行对象是 checklistItems。

button.setOnLongClickListener(new View.OnLongClickListener() {
        public boolean onLongClick(View v) {
            ArrayList<Checklist> temp = new ArrayList<Checklist>();
            for (int i = checklistItems.size()-1; i >= 0; i--){
                if (checklistItems.get(i).getValue() != 1)
                    temp.add(checklistItems.get(i));
            }

            checklistItems = temp;
            myAdapter.notifyDataSetChanged();

            return true;
        }
    });

我确信我过滤掉不需要的项目的程序是好的......除非它不是哈哈。我只是不明白为什么它会这样。任何帮助表示赞赏!

public class CustomAdapter extends ArrayAdapter<Checklist> {
ArrayList<Checklist> checklistItems;
Context context;

public CustomAdapter(Context context, ArrayList<Checklist> resource){
    super(context, R.layout.list_view_row_item, resource);
    this.context = context;
    this.checklistItems = resource;
}
@Override
public View getView(int position, View convertView, ViewGroup parent){
    LayoutInflater inflater = ((Activity)context).getLayoutInflater();
    convertView = inflater.inflate(R.layout.list_view_row_item, parent, false);
    TextView name = (TextView) convertView.findViewById(R.id.itemText);
    CheckBox cb = (CheckBox) convertView.findViewById(R.id.checkBox);

    name.setText(checklistItems.get(position).getName());
    if (checklistItems.get(position).getValue() == 1)
        cb.setChecked(true);
    else
        cb.setChecked(false);
    return convertView;
}

编辑:初始化适配器的 onCreate 方法:

public class MainActivity extends Activity {
private ListView lv;
ArrayList<Checklist> checklistItems;
CustomAdapter myAdapter;
Button button;


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

//读取项目();

    button = (Button) findViewById(R.id.addItem);
    button.setOnClickListener(new View.OnClickListener() {
        public void onClick(View v) {
            shortclick();
        }
    });

    button.setOnLongClickListener(new View.OnLongClickListener() {
        public boolean onLongClick(View v) {
            ArrayList<Checklist> temp = new ArrayList<Checklist>();
            for (int i = checklistItems.size()-1; i >= 0; i--){
                if (checklistItems.get(i).getValue() == 1) // changed to == 1
                    temp.add(checklistItems.get(i));
            }

            //checklistItems = temp; //Don't change reference of Adapter data source

            checklistItems.clear(); //added
            checklistItems.addAll(temp); //added

            myAdapter.notifyDataSetChanged();

            return true;
        }
    });


    lv = (ListView) findViewById(R.id.listView);
    checklistItems = new ArrayList<Checklist>();
    checklistItems.add(new Checklist(0,"When you add a new item it will show here"));
    checklistItems.add(new Checklist(0,"Check the items that you've finished"));

    myAdapter = new CustomAdapter(this,checklistItems);
    lv.setAdapter(myAdapter);


}

shortClick 方法:

    public void shortclick()
{
    EditText taskET = (EditText) findViewById(R.id.taskET);
    String itemText = taskET.getText().toString();
    Checklist newTask = new Checklist(0,itemText);
    myAdapter.add(newTask);
    taskET.setText("");

}

list 类:

public class Checklist {
int value;
String text;
boolean isChecked;

public Checklist(int value, String text){
    this.value = value;
    this.text = text;
}

public String getName(){
    return this.text;
}

public int getValue(){
    return this.value;
}

public void setValue(boolean isChecked){
    if (value == 1)
       isChecked = true;
    else
        isChecked = false;
}

Answer 1

一旦 Adapter 被设置为数据源，您就无法更改其数据源的引用。

获得所需结果的最简单方法是在数据源上调用 clear()，然后调用 addAll() 将新数据添加到原始数据来源。

button.setOnLongClickListener(new View.OnLongClickListener() {
    public boolean onLongClick(View v) {
        ArrayList<Checklist> temp = new ArrayList<Checklist>();
        for (int i = 0; i < checklistItems.size(); i++){
            if (checklistItems.get(i).getValue() == 0)
                temp.add(checklistItems.get(i));
        }

        //checklistItems = temp; //Don't change reference of Adapter data source

        checklistItems.clear(); //added
        checklistItems.addAll(temp); //added

        myAdapter.notifyDataSetChanged();

        return true;
    }
});

编辑，您还需要使用复选框的监听器更新数据，如下所示:

    @Override
    public View getView(int position, View convertView, ViewGroup parent){
        LayoutInflater inflater = ((Activity)context).getLayoutInflater();
        convertView = inflater.inflate(R.layout.list_view_row_item, parent, false);
        TextView name = (TextView) convertView.findViewById(R.id.itemText);
        CheckBox cb = (CheckBox) convertView.findViewById(R.id.checkBox);

        cb.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
            @Override
            public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
                checklistItems.get(position).setValue(isChecked);
            }
        });

        name.setText(checklistItems.get(position).getName());
        if (checklistItems.get(position).getValue() == 1)
            cb.setChecked(true);
        else
            cb.setChecked(false);
        return convertView;
    }