第5章（6） 状态切换（Switch）和评级条（RatingBar）

分类：C#、Android、VS2015；

创建日期：2016-02-07

一、简介

1、利用Switch或者ToggleButton切换状态

如果只有两种状态，可以用ToggleButton控件或Switch控件切换这两种状态。如下图所示（左侧是ToggleButton的效果，右侧是从API 19开始增加的Switch的效果）：

2、利用五角星评级条（RatingBar）设置评级

【NumStars】属性：定义星级的个数。

【StepSize】属性：定义每一颗星的粒度（值为 0.5 将允许半星级评级)。

【RatingBarChange】事件：星级发生变化时引发。

例如：

<RatingBar android:id="@+id/ratingbar"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:numStars="5"

android:stepSize="1.0"/>

二、示例6—Demo06SwitchAndRatingBar

1、运行效果：

2、添加demo06_SwitchAndRatingBar.axml文件

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    <Button
        android:id="@+id/button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:padding="10dp"
        android:background="@drawable/android_button" />
    <EditText
        android:id="@+id/edittext"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content" />
    <CheckBox
        android:id="@+id/checkbox"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="check it out" />
    <RadioGroup
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical">
        <RadioButton
            android:id="@+id/radio_red"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Red" />
        <RadioButton
            android:id="@+id/radio_blue"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Blue" />
    </RadioGroup>
    <Switch
        android:id="@+id/togglebutton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="允许开启XX功能码？"
        android:checked="true" />
    <RatingBar
        android:id="@+id/ratingbar"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:numStars="5"
        android:stepSize="1.0" />
</LinearLayout>

3、添加Demo06SwitchAndRatingBar.cs文件

using System;
using Android.App;
using Android.OS;
using Android.Views;
using Android.Widget;

namespace ch05demos.SrcActivity
{
    [Activity(Label = "SwitchAndRatingBarDemo")]
    public class Demo06SwitchAndRatingBar : Activity
    {
        protected override void OnCreate(Bundle savedInstanceState)
        {
            base.OnCreate(savedInstanceState);
            SetContentView(Resource.Layout.demo06_SwitchAndRatingBar);

            Button button = FindViewById<Button>(Resource.Id.button);
            button.Click += delegate
            {
                Toast.MakeText(this, "Beep Boop", ToastLength.Short).Show();
            };

            var editText = FindViewById<EditText>(Resource.Id.edittext);
            //---------------------------------------------------------
            //技巧：按+=后，连续按两次<Tab>键，就会自动生成事件处理程序
            //---------------------------------------------------------
            editText.KeyPress += EditText_KeyPress;

            var checkbox = FindViewById<CheckBox>(Resource.Id.checkbox);
            checkbox.Click += delegate
            {
                if (checkbox.Checked)
                    Toast.MakeText(this, "Selected", ToastLength.Short).Show();
                else
                    Toast.MakeText(this, "Not selected", ToastLength.Short).Show();
            };

            var radioRed = FindViewById<RadioButton>(Resource.Id.radio_red);
            var radioBlue = FindViewById<RadioButton>(Resource.Id.radio_blue);
            radioRed.Click += Radio_Click;
            radioBlue.Click += Radio_Click;

            Switch toggleButton = FindViewById<Switch>(Resource.Id.togglebutton);
            toggleButton.Click += (o, e) => {
                if (toggleButton.Checked)
                    Toast.MakeText(this, "Checked", ToastLength.Short).Show();
                else
                    Toast.MakeText(this, "Not checked", ToastLength.Short).Show();
            };

            RatingBar ratingbar = FindViewById<RatingBar>(Resource.Id.ratingbar);
            ratingbar.RatingBarChange += (o, e) => {
                Toast.MakeText(this, "New Rating: " + ratingbar.Rating.ToString(), ToastLength.Short).Show();
            };
        }

        private void EditText_KeyPress(object sender, View.KeyEventArgs e)
        {
            var editText = sender as EditText;
            e.Handled = false;
            if (e.Event.Action == KeyEventActions.Down && e.KeyCode == Keycode.Enter)
            {
                Toast.MakeText(this, editText.Text, ToastLength.Short).Show();
                e.Handled = true;
            }
        }

        private void Radio_Click(object sender, EventArgs e)
        {
            RadioButton r = sender as RadioButton;
            Toast.MakeText(this, r.Text, ToastLength.Short).Show();
        }
    }
}

运行观察效果。