在购物车中，点击加 减号，改变购买的商品数量的监听器

//给加号减号IamgeView添加监听
// i是 每个购物项的position  下标
//holder.ivm   减号的控件
//holder.ivp   加号的控件
holder.ivm.setOnClickListener(new ModifyNumListener(i, ModifyNumListener.BUTTON_MINUS));
holder.ivp.setOnClickListener(new ModifyNumListener(i, ModifyNumListener.BUTTON_PLUS));

/** 在购物车中 点击加 减号，改变购买的商品数量的 监听器
* 设置点击加号  减号的监听器
*/
class ModifyNumListener implements View.OnClickListener {
// 声明的常量
public static final int BUTTON_PLUS = 1;
public static final int BUTTON_MINUS = 2;

private int position;
private int type;

ModifyNumListener(int position, int type) {
this.position = position;
this.type = type;
}

@Override
public void onClick(View view) {
TextView tvNum = (TextView) listView.findViewWithTag("tvNum" + position);
TextView tvCount = (TextView) listView.findViewWithTag("tvCount" + position);
int number = Integer.parseInt(tvNum.getText().toString());
switch (type) {
case BUTTON_PLUS:
number++;
tvNum.setText(number+"");
tvCount.setText("x" + number);
break;
case BUTTON_MINUS:
number = number==1?number:number-1;
tvNum.setText(number+"");
tvCount.setText("x" + number);
break;
}
presenter.modifyNum(getItem(position).getBook().getId(), number);
}
}

public void setPresenter(ICartPresenter presenter){
this.presenter = presenter;
}