微信小程序之支付密码输入demo

在小程序中实现支付密码的输入，要解决几个问题：
1、小程序要想唤起键盘，必须要借助input控件。通过input控件和其属性focus来唤起和隐藏输入键盘。
2、要让input控件不可见。让光标和输入的字符都不可见，这里是把input控件定位到左边不可见范围。
先看实现后的效果图：

095615iwk4jtk24w2hvjhq.gif

实现demo代码：
wxml

<view catchtap='showInputLayer' class="btn_pay">立即支付</view>
<!-- 密码输入框 -->
<view wx:if='{{showPayPwdInput}}'>
    <view class='bg_layer'></view>
    <view class='input_main'>
        <view class='input_title'>
            <view class='input_back' catchtap='hidePayLayer'><text></text></view>
            <text>输入支付密码</text>
        </view>
        <view class='input_tip'><text>使用会员卡余额支付需要验证身份，验证通过后才可进行支付。</text></view>
        <view class='input_row' catchtap='getFocus'>
            <view class='pwd_item' wx:for='{{6}}' wx:key='item' wx:for-index='i'>
                <text wx:if='{{pwdVal.length>i}}'></text>
            </view>
        </view>
        <view class='forget_pwd' catchtap='hidePayLayer'>忘记密码</view>
        <input class='input_control' password type='number' focus='{{payFocus}}' bindinput='inputPwd' maxlength='6'/>
    </view>
</view>

js

//获取应用实例
const app = getApp()
Page({
  data: {
    showPayPwdInput: false,  //是否展示密码输入层
    pwdVal: '',  //输入的密码
    payFocus: true, //文本框焦点
  },
  onLoad: function () {
    this.showInputLayer();
  },
  /**
   * 显示支付密码输入层
   */
  showInputLayer: function(){
    this.setData({ showPayPwdInput: true, payFocus: true });
  },
  /**
   * 隐藏支付密码输入层
   */
  hidePayLayer: function(){
    var val = this.data.pwdVal;
    this.setData({ showPayPwdInput: false, payFocus: false, pwdVal: '' }, function(){
      wx.showToast({
        title: val,
      })
    });
  },
  /**
   * 获取焦点
   */
  getFocus: function(){
    this.setData({ payFocus: true });
  },
  /**
   * 输入密码监听
   */
  inputPwd: function(e){
      this.setData({ pwdVal: e.detail.value });
      if (e.detail.value.length >= 6){
        this.hidePayLayer();
      }
  }
})

wxss

.btn_pay{
  margin: 100rpx auto; width: 600rpx; height: 100rpx; line-height: 100rpx; border-radius: 100rpx;
  background-color: #d3a95a; color: #fff; font-size: 36rpx; text-align: center; 
}
/* 支付密码css start */
.bg_layer{
  position: fixed; left: 0; top: 0; bottom: 0; right: 0;
  background-color: rgba(0, 0, 0, 0.6); z-index: 9998;
}
.input_main{
    position: fixed; left: 0; bottom: 500rpx; width: 100%; height: 394rpx;
    background-color: #fff; z-index: 9999;
}
.input_title{
    width: 100%; height: 90rpx; line-height: 90rpx; text-align: center; 
    font-size: 32rpx; border-bottom: 1rpx solid #e2e2e2;
}
.input_back{
    position: absolute; left: 0; top: 0;
    width: 80rpx; height: 90rpx; display: flex; justify-content: center; align-items: center;
}
.input_back text{
  width: 20rpx;
  height: 20rpx;
  background-color: white;
  border: 1rpx solid #aaa;
  border-width: 5rpx 0 0 5rpx;
  transform: rotate(-45deg);
}
.input_tip{  margin: 30rpx; font-size: 24rpx; color: #888; }
/* 密码掩码模拟 */
.input_row{
  width: 690rpx; margin: 0 auto; height: 98rpx; position: relative;
  display: flex; align-items: center; border: 1rpx solid #e2e2e2; border-radius: 20rpx;
}
.input_row .pwd_item{
  flex: 1; display: flex; align-items: center; justify-content: center; 
  height: 100%; border-right: 1rpx solid #e2e2e2; position: relative;
}
.pwd_item:nth-last-of-type(1) { border-right: 0; } 
.pwd_item text { 
  width: 30rpx; height: 30rpx; border-radius: 30rpx; background-color: #555;
}
.forget_pwd{ 
  float: right; margin: 30rpx; width: 100rpx; text-align: right; font-size: 24rpx; color: #ff7800;
}
/* 文本输入框位置: 设置到左边隐藏 */
.input_control { 
  position: relative; left: -300rpx; bottom: 0; width: 100rpx; height: 100rpx;
}