C#开发Android移动应用系列之调用手机摄像头拍照

继续分享通过Xamarin开发Android应用的案例：调用手机摄像头拍照

1. 新建一个内容页Page3并通过路由注册，方法与之前相同，略过

2. 在内容页Page3.xaml上放一个Image和一个Button

<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             x:Class="XamarinApp1.Views.Page3">
    <ContentPage.Content>
        <StackLayout>
            <Grid>
                <Grid.RowDefinitions>
                    <RowDefinition Height="500"></RowDefinition>
                </Grid.RowDefinitions>
                <Image Source="" x:Name="imageview" Grid.Row="0" HeightRequest="500" WidthRequest="500"/>
            </Grid>
            <Button Text="Shoot" Clicked="Button3_Clicked"/>

        </StackLayout>
    </ContentPage.Content>
</ContentPage>

3. 在Page3.xaml.cs上编写按钮点击事件

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

using Xamarin.Forms;
using Xamarin.Forms.Xaml;
using Xamarin.Essentials;
using System.IO;
using XamarinApp1.ViewModels;

namespace XamarinApp1.Views
{
	[XamlCompilation(XamlCompilationOptions.Compile)]
	public partial class Page3 : ContentPage
	{
       
		public Page3 ()
		{
			InitializeComponent ();
        
		}

		public async void Button3_Clicked(object sender, EventArgs e)
		{
            // 检查是否支持相机
            if (!MediaPicker.IsCaptureSupported)
            {
                await DisplayAlert("Error", "相机不可用", "OK");
                return;
            }

            // 获取图像
            var options = new MediaPickerOptions
            {
                Title = "拍照"
            };
            var photo = await MediaPicker.CapturePhotoAsync(options);

            // 获取图像的字节数据
            using (var stream = await photo.OpenReadAsync())
            {
                var buffer = new byte[stream.Length];
                await stream.ReadAsync(buffer, 0, (int)stream.Length);

                // 这里可以对图像数据进行处理

                // 显示图像
                var im = new Image { Source = ImageSource.FromStream(() => new MemoryStream(buffer)) };
                // 将图像显示在你的界面上
                imageview.Source = im.Source;
            }
        }

	}

	
}

4. 要调用手机摄像头需设置手机权限，在Properties下的AndroidManifest.xml中

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android" android:versionCode="1" android:versionName="1.0" package="com.companyname.xamarinapp1" android:installLocation="preferExternal">
	<uses-sdk android:minSdkVersion="21" android:targetSdkVersion="29" />
	<application android:label="XamarinApp1.Android" android:theme="@style/MainTheme"></application>
	<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
	<uses-permission android:name="android.permission.BATTERY_STATS" />
	<uses-permission android:name="android.permission.CAMERA" />
	<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
	<uses-permission android:name="android.permission.MANAGE_EXTERNAL_STORAGE" />
	<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
</manifest>

5. 在MainActivity.cs中处理权限请求

using System;

using Android.App;
using Android.Content.PM;
using Android.Runtime;
using Android.OS;
using AndroidX.Core.App;
using Android;

namespace XamarinApp1.Droid
{
    [Activity(Label = "XamarinApp1", Icon = "@mipmap/icon", Theme = "@style/MainTheme", MainLauncher = true, ConfigurationChanges = ConfigChanges.ScreenSize | ConfigChanges.Orientation | ConfigChanges.UiMode | ConfigChanges.ScreenLayout | ConfigChanges.SmallestScreenSize )]
    public class MainActivity : global::Xamarin.Forms.Platform.Android.FormsAppCompatActivity
    {
        const int RequestStorageWriteId = 0; // 这里的值可以是任意整数，只要确保唯一就可以

        protected override void OnCreate(Bundle savedInstanceState)
        {
            base.OnCreate(savedInstanceState);
            // 请求存储写入权限
            if (CheckSelfPermission(Manifest.Permission.WriteExternalStorage) != (int)Permission.Granted)
            {
                ActivityCompat.RequestPermissions(this, new string[] { Manifest.Permission.WriteExternalStorage }, RequestStorageWriteId);
            }
            Xamarin.Essentials.Platform.Init(this, savedInstanceState);
            global::Xamarin.Forms.Forms.Init(this, savedInstanceState);
            LoadApplication(new App());
        }
        public override void OnRequestPermissionsResult(int requestCode, string[] permissions, [GeneratedEnum] Android.Content.PM.Permission[] grantResults)
        {
            Xamarin.Essentials.Platform.OnRequestPermissionsResult(requestCode, permissions, grantResults);

            base.OnRequestPermissionsResult(requestCode, permissions, grantResults);
            
        }
    }
}