Xamarin.Android 的照相機使用

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Android 提供了不少硬體功能。其中照相機功能更是兵家必爭之地。
甚至爆發如「三星門」等事件。不過本篇文章的目的只呼叫Android系統定義的API，取得相片後顯示出來。

現在我們先引入幾個 Android 負責處理 Camera 的命名空間。
當然會多些，不過要是在 Visual Studio 內開發的同學，很快就可以用工具移除。

using System;using System.Linq;using System.Text;using System.Collections.Generic;using Android.OS;using Android.App;using Android.Views;using Android.Widget;using Android.Content;using Android.Runtime;using Android.Graphics;using Android.Provider;using Android.Content.PM;using Java.IO;using Environment = Android.OS.Environment;using Uri = Android.Net.Uri;

我們先檢查硬體配備是否已準備好？

private bool IsThereAnAppToTakePictures (){　　Intent intent = new Intent (MediaStore.ActionImageCapture);   IList<ResolveInfo> availableActivities = PackageManager.QueryIntentActivities (intent, PackageInfoFlags.MatchDefaultOnly);   return availableActivities != null && availableActivities.Count > 0;}

特別請大家注意

Intent intent = new Intent (MediaStore.ActionImageCapture);

在這邊我們使用系統提供的 Intent 來取得照相機的功能。

然後我們準備存儲目錄

private void CreateDirectoryForPictures (){    App._dir = new File (    Environment.GetExternalStoragePublicDirectory ( Environment.DirectoryPictures), "AndroidTips");    if (!App._dir.Exists ())    {        bool result =App._dir.Mkdirs( );        Debug.WriteLine ("mkdir:" + result);    }}      

準備處理 Bitmap 的方法（改變大小確保能按比例顯示）

public static class BitmapHelpers{　　public static Bitmap LoadAndResizeBitmap (this string fileName, int width, int height)   {　　　　// First we get the the dimensions of the file on disk       BitmapFactory.Options options = new BitmapFactory.Options { InJustDecodeBounds = true };       BitmapFactory.DecodeFile (fileName, options);       int outHeight = options.OutHeight;       int outWidth = options.OutWidth;       int inSampleSize = 1;       if (outHeight > height || outWidth > width)       {       　　inSampleSize = outWidth > outHeight          　　? outHeight / height : outWidth / width;       }       // Now we will load the image and have BitmapFactory resize it for us.       options.InSampleSize = inSampleSize;       options.InJustDecodeBounds = false;       Bitmap resizedBitmap = BitmapFactory.DecodeFile (fileName, options);       return resizedBitmap;　　}}

 

準備回調的方法

protected override void OnActivityResult (int requestCode, Result resultCode, Intent data){    base.OnActivityResult (requestCode, resultCode, data);    // Make it available in the gallery    Intent mediaScanIntent = new Intent (Intent.ActionMediaScannerScanFile);    Uri contentUri = Uri.FromFile (App._file);    mediaScanIntent.SetData (contentUri);    SendBroadcast (mediaScanIntent);    // Display in ImageView. We will resize the bitmap to fit the display.    // Loading the full sized image will consume to much memory    // and cause the application to crash.    int height = Resources.DisplayMetrics.HeightPixels;    int width = resultImageView.Height ;    App.bitmap = App._file.Path.LoadAndResizeBitmap (width, height);    if (App.bitmap != null) {        resultImageView.SetImageBitmap (App.bitmap);        Debug.WriteLine ("contentUri:" + contentUri);        App.bitmap = null;    }    // Dispose of the Java side bitmap.    GC.Collect();}

 

如此即可快速調用照相機的功能。

參考資料：https://developer.xamarin.com/recipes/android/other_ux/camera_intent/take_a_picture_and_save_using_camera_app/

Xamarin.Android 的照相機使用