如何从 BaseAdapter 中的 NumberPicker 设置 OnValueChangedListener

Question

我正在尝试创建一个 BaseAdapter，其中每个元素都有一个 NumberPicker 和一个 Button。按钮的动作参数取决于 NumberPicker 中选取的值。我认为的一种解决方案是在 NumberPicker 的 onValueChange 内创建一个 setOnClickListener（按钮的），问题是当我更改数字时 onValueChange 永远不会被触发。

我把代码留给你，让它更清楚：

public class Adapter extends BaseAdapter{
...

  public View getView(int position, View convertView, ViewGroup parent) {
        View v = convertView;
        if (v == null)
        {
            LayoutInflater vi = (LayoutInflater) con.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            v = vi.inflate(R.layout.row, null);
        }
        button = (Button) v.findViewById(R.id.button);
        numPick = (NumberPicker) v.findViewById(R.id.numPick);
        numPick.setOnValueChangedListener(new NumberPicker.OnValueChangeListener() {
            public void onValueChange(NumberPicker picker, int oldVal, int newVal) {
                val = newVal;
                button.setOnClickListener(new View.OnClickListener() {
                    public void onClick(View arg0) {
                        actionToPerform(val);
                    }
                });
            }
        });

我该如何解决这个问题？谢谢！

Answer 1

由于适配器将重用布局，因此您需要在创建布局时设置监听器。将按钮侦听器移出。否则，它将在每次值更改时设置。这是修改后的代码：

// Put the array as a member of your activity or fragment's class
// Remember to save it between life cycle event
// Initialize it to same size as your adapter data
int[] numValues;

public View getView(int position, View convertView, ViewGroup parent) {
    View v = convertView;
    if (v == null)
    {
        LayoutInflater vi = (LayoutInflater) con.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        v = vi.inflate(R.layout.row, null);

        final Button button = (Button) v.findViewById(R.id.button);
        final NumberPicker numPick = (NumberPicker) v.findViewById(R.id.numPick);

        button.setOnClickListener(new View.OnClickListener() {
                public void onClick(View arg0) {
                    // Get the position value from the tag field
                    int pos = (int)button.tag;
                    actionToPerform(numValues[pos]);
                }
            });

        numPick.setOnValueChangedListener(new NumberPicker.OnValueChangeListener() {
        public void onValueChange(NumberPicker picker, int oldVal, int newVal) {
              // Save the value in the number picker
              numPick.tag = newVal;
          }
        });
    }

    // Save the position in the button's tag field
    button.tag = position;
    // Restore picker value
    final NumberPicker numPick1 = (NumberPicker) v.findViewById(R.id.numPick);
    numPicker1.setValue(numValues[position]);

}

在标签字段中保存数据将确保您在单击按钮时获得正确的行数据。我不知道你的数据是如何表示的，所以我引入了一个 int 数组来存储这些值。否则，选择器在被重用时将失去价值。