~楓花雪岳~: [X.Andriod] 從 Asset 來顯示圖片

星期二, 6月 07, 2016

[X.Andriod] 從 Asset 來顯示圖片

查詢 ImageView.SetImageURI 語法時，查到 Visual C#與Xamarin跨平台行動App開發實戰書籍內範例 - Asset 內圖片載進 Andriod 系統內，再把檔案顯示在 ImageView 內，就拿來練習囉

Main.axml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent">
    <Button
        android:id="@+id/MyButton"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="讀取 Asset 圖片" />
    <TextView
        android:text="Text"
        android:layout_width="match_parent"
        android:layout_height="100.0dp"
        android:id="@+id/textView1" />
    <ImageView
        android:src="@drawable/xamarinicon"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:id="@+id/imageView1"
        android:layout_marginTop="0.0dp"
        android:layout_marginBottom="0.0dp" />
</LinearLayout>

MainActivity.cs

using System.IO;
using System.Text;

namespace ImageViewAssets
{
    [Activity(Label = "ImageViewAssets", MainLauncher = true, Icon = "@drawable/icon")]
    public class MainActivity : Activity
    {
        protected override void OnCreate(Bundle bundle)
        {
            base.OnCreate(bundle);
            SetContentView(Resource.Layout.Main);

            Button button = FindViewById<Button>(Resource.Id.MyButton);
            ImageView image = FindViewById<ImageView>(Resource.Id.imageView1);
            TextView text = FindViewById<TextView>(Resource.Id.textView1);
            button.Click += (Sender, e) =>
            {
                string TargetPath = @"DemoDir/DemoDir2";
                string[] result = Assets.List(TargetPath);

                // 產生隨機整數
                Random r = new Random(Guid.NewGuid().GetHashCode());
                int IndexID = r.Next(0, result.Length);

                string fileName = result[IndexID].ToString();
                string fileFullName = Path.Combine(TargetPath, fileName);
                string fileDriodFullName = Path.Combine(FilesDir.Path, fileName);

                StringBuilder builder = new StringBuilder();
                builder.AppendLine($"Aseet 檔案名稱：{fileName}");
                builder.AppendLine($"Asset 檔案完整路徑：{fileFullName}");
                builder.AppendLine($"Driod 檔案完整路應：{fileDriodFullName}");
                text.Text = builder.ToString();

                using (var stream = Assets.Open(fileFullName))
                using (var file = File.Create(fileDriodFullName))
                {
                    stream.CopyTo(file);
                }

                image.SetImageURI(Android.Net.Uri.Parse(fileDriodFullName));
            };
        }
    }
}

Asset

Asset 官方解釋

Assets provide a way to include arbitrary files like text, xml, fonts, music, and video in your application. If you try to include these files as "resources", Android will process them into its resource system and you will not be able to get the raw data. If you want to access data untouched, Assets are one way to do it.

Assets added to your project will show up just like a file system that can read from by your application using AssetManager.

原以為 Asset 會如同 Drawable 一樣可以透過 Reflection 來取得裡面的檔案，沒想到 Asset 不是 Class，Asset 內資料是存在 APK 內，要透過 AssetManager 來取得