在 Xamarin.Forms 中，我们通常使用 TableView 来构建输入表单。Xamarin 为我们提供了 EntryCell 用于输入文本，但是其并不支持密码输入，即密码掩码。这里要对 EntryCell 进行扩展，使其支持密码输入。
首先，我们需要在共享项目（多平台项目）中增加控件定义，我们称之为：ExtendedEntryCell
1 /// <summary>
2 /// An extended entry cell control that allows set IsPassword
3 /// </summary>
4 public class ExtendedEntryCell : EntryCell
5 {
6
7 /// <summary>
8 /// The IsPassword property
9 /// </summary>
10 public static readonly BindableProperty IsPasswordProperty = BindableProperty.Create<ExtendedEntryCell, bool>(p => p.IsPassword, false);
11
12 /// <summary>
13 /// Gets or sets IsPassword
14 /// </summary>
15 public bool IsPassword
16 {
17 get { return (bool)GetValue(IsPasswordProperty); }
18 set { SetValue(IsPasswordProperty, value); }
19 }
20 }
我们需要在Android和iOS中加入各自的Render。
Android 平台的 Render：
1 using Android.Content;
2 using Android.Text.Method;
3 using Android.Views;
4 using Android.Widget;
5 using WsLink.App.Controls;
6 using Xamarin.Forms;
7 using Xamarin.Forms.Platform.Android;
8 using View = Android.Views.View;
9
10 [assembly: ExportRenderer(typeof(ExtendedEntryCell), typeof(ExtendedEntryCellRenderer))]
11
12 namespace App.Controls
13 {
14 public class ExtendedEntryCellRenderer : EntryCellRenderer
15 {
16 protected override View GetCellCore(Cell item, View convertView, ViewGroup parent, Context context)
17 {
18 var cell = base.GetCellCore(item, convertView, parent, context);
19 var textField = (cell as EntryCellView)?.EditText as TextView;
20
21 if (textField != null && textField.TransformationMethod != PasswordTransformationMethod.Instance)
22 {
23 textField.TransformationMethod = PasswordTransformationMethod.Instance;
24 }
25 return cell;
26 }
27 }
28 }
iOS 平台的 Render
1 using UIKit;
2 using WsLink.App.Controls;
3 using Xamarin.Forms;
4 using Xamarin.Forms.Platform.iOS;
5
6 [assembly: ExportRenderer(typeof(ExtendedEntryCell), typeof(ExtendedEntryCellRenderer))]
7
8 namespace WsLink.App.Controls
9 {
10 public class ExtendedEntryCellRenderer : EntryCellRenderer
11 {
12 public override UITableViewCell GetCell(Cell item, UITableViewCell reusableCell, UITableView tv)
13 {
14 var entryCell = (ExtendedEntryCell) item;
15 var cell = base.GetCell(item, reusableCell, tv);
16 if (cell != null)
17 {
18 var textField = (UITextField) cell.ContentView.Subviews[0];
19 textField.SecureTextEntry = entryCell.IsPassword;
20 }
21 return cell;
22 }
23 }
24 }
使用方法
<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
xmlns:controls="clr-namespace:WsLink.App.Controls"
x:Class="App.Account.LoginPage" Title="登录">
<TableView Intent="Form">
<TableSection>
<EntryCell Label="账户" Placeholder="账户" Text="{Binding Username}"></EntryCell>
<controls:ExtendedEntryCell IsPassword="True" Label="密码" Placeholder="密码" Text="{Binding Password}"></controls:ExtendedEntryCell>
</Ta