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：

实现demo代码：

1、页面代码

1. <view catchtap='showInputLayer' class="btn_pay">立即支付</view>
2. <!-- 密码输入框 -->
3. <view wx:if='{{showPayPwdInput}}'>
4. <view class='bg_layer'></view>
5. <view class='input_main'>
6. <view class='input_title'>
7. <view class='input_back' catchtap='hidePayLayer'><text></text></view>
8. <text>输入支付密码</text>
9. </view>
10. <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>
11. <view class='input_row' catchtap='getFocus'>
12. <view class='pwd_item' wx:for='{{6}}' wx:key='item' wx:for-index='i'>
13. <text wx:if='{{pwdVal.length>i}}'></text>
14. </view>
15. </view>
16. <view class='forget_pwd' catchtap='hidePayLayer'>忘记密码</view>
17. <input class='input_control' password type='number' focus='{{payFocus}}' bindinput='inputPwd' maxlength='6'/>
18. </view>
19. </view>

2、js代码

1. //index.js
2. //获取应用实例
3. const app = getApp()
4.  
5. Page({
6. data: {
7. showPayPwdInput: false, //是否展示密码输入层
8. pwdVal: '', //输入的密码
9. payFocus: true, //文本框焦点
10. },
11. onLoad: function () {
12. this.showInputLayer();
13. },
14. /**
15. * 显示支付密码输入层
16. */
17. showInputLayer: function(){
18. this.setData({ showPayPwdInput: true, payFocus: true });
19. },
20. /**
21. * 隐藏支付密码输入层
22. */
23. hidePayLayer: function(){
24.  
25. var val = this.data.pwdVal;
26.  
27. this.setData({ showPayPwdInput: false, payFocus: false, pwdVal: '' }, function(){
28. wx.showToast({
29. title: val,
30. })
31. });
32.  
33. },
34. /**
35. * 获取焦点
36. */
37. getFocus: function(){
38. this.setData({ payFocus: true });
39. },
40. /**
41. * 输入密码监听
42. */
43. inputPwd: function(e){
44. this.setData({ pwdVal: e.detail.value });
45.  
46. if (e.detail.value.length >= 6){
47. this.hidePayLayer();
48. }
49. }
50. })

3、样式

1. .btn_pay{
2. margin: 100rpx auto; width: 600rpx; height: 100rpx; line-height: 100rpx; border-radius: 100rpx;
3. background-color: #d3a95a; color: #fff; font-size: 36rpx; text-align: center;
4. }
5. /* 支付密码css start */
6. .bg_layer{
7. position: fixed; left: 0; top: 0; bottom: 0; right: 0;
8. background-color: rgba(0, 0, 0, 0.6); z-index: 9998;
9. }
10. .input_main{
11. position: fixed; left: 0; bottom: 500rpx; width: 100%; height: 394rpx;
12. background-color: #fff; z-index: 9999;
13. }
14. .input_title{
15. width: 100%; height: 90rpx; line-height: 90rpx; text-align: center;
16. font-size: 32rpx; border-bottom: 1rpx solid #e2e2e2;
17. }
18. .input_back{
19. position: absolute; left: 0; top: 0;
20. width: 80rpx; height: 90rpx; display: flex; justify-content: center; align-items: center;
21. }
22. .input_back text{
23. width: 20rpx;
24. height: 20rpx;
25. background-color: white;
26. border: 1rpx solid #aaa;
27. border-width: 5rpx 0 0 5rpx;
28. transform: rotate(-45deg);
29. }
30.  
31. .input_tip{ margin: 30rpx; font-size: 24rpx; color: #888; }
32.  
33. /* 密码掩码模拟 */
34. .input_row{
35. width: 690rpx; margin: 0 auto; height: 98rpx; position: relative;
36. display: flex; align-items: center; border: 1rpx solid #e2e2e2; border-radius: 20rpx;
37. }
38. .input_row .pwd_item{
39. flex: 1; display: flex; align-items: center; justify-content: center;
40. height: 100%; border-right: 1rpx solid #e2e2e2; position: relative;
41. }
42. .pwd_item:nth-last-of-type(1) { border-right: 0; }
43. .pwd_item text {
44. width: 30rpx; height: 30rpx; border-radius: 30rpx; background-color: #555;
45. }
46.  
47.  
48. .forget_pwd{
49. float: right; margin: 30rpx; width: 100rpx; text-align: right; font-size: 24rpx; color: #ff7800;
50. }
51.  
52. /* 文本输入框位置: 设置到左边隐藏 */
53. .input_control {
54. position: relative; left: -300rpx; bottom: 0; width: 100rpx; height: 100rpx;
55. }