如何在运行时将图库中的图像绑定到imageView？

Question

我有一个关于做whatsapp克隆的作业。但是我有一个问题。我有一个添加联系人屏幕。用户从图库中选择图像，然后输入其名称。当他们单击添加按钮时，列表项将被添加到聊天活动中。屏幕截图如下。我有一个人类，如：

public class Person
{
private int id;
private string name;
private int imageId;

public Person(int id, string name, int imageId)
{
    this.id = id;
    this.name = name;
    this.imageId = imageId;

}


public int Id   // property
{
    get { return id; }   // get method
    set { id = value; }  // set method
}

public string Name   // property
{
    get { return name; }   // get method
    set { name = value; }  // set method
}


public int ImageId   // property
{
    get { return imageId; }   // get method
    set { imageId = value; }  // set method
}

public static explicit operator Java.Lang.Object(Person v)
{
    throw new NotImplementedException();
}

}

public class PersonAdapter : BaseAdapter
{
private LayoutInflater mInflater;
private List<Person> personArrayList;

public PersonAdapter(Activity activity, List<Person> personArrayList)
{

    this.mInflater = (LayoutInflater)activity.GetSystemService(Context.LayoutInflaterService);
    this.personArrayList = personArrayList;
}

public override int Count => personArrayList.Count;

public override Object GetItem(int position)
{
    return (Object)personArrayList.ElementAt(position);
}

public override long GetItemId(int position)
{
    return position;
}

public override View GetView(int position, View convertView, ViewGroup parent)
{
    convertView = mInflater.Inflate(Resource.Layout.List_Item, null);
    TextView personName = (TextView)convertView.FindViewById(Resource.Id.name);
    TextView personMessage = (TextView)convertView.FindViewById(Resource.Id.message);
    ImageView personImage = (ImageView)convertView.FindViewById(Resource.Id.imageView);
    Person person = personArrayList.ElementAt(position);
    personName.Text = person.Name;
    if(MainActivity.messages[person.Id].Count != 0)
        {
            personMessage.Text = MainActivity.messages[person.Id][MainActivity.messages[person.Id].Count - 1];
        }
    else
        {
            personMessage.Text = "";
        }
    personImage.SetImageResource(person.ImageId);
    return convertView;
}
}
}

我有一个personAdapter类，聊天活动只有listView。所以我通过适配器将列表绑定到listView。我手动添加了一些人以查看聊天菜单。如果我将图像添加到可绘制文件夹，则没有问题。但是我如何添加图像来创建新的人。我无法在运行时将图像添加到drawable。当我尝试从外部存储读取图像时。他们没有资源ID。因此，人类不接受。

{
[Activity(Label = "@string/app_name", Theme = "@style/AppTheme", MainLauncher = true)]
public class MainActivity : AppCompatActivity
{
    public static List<Person> persons = new List<Person>();
    public static Dictionary<int, List<string>> messages = new Dictionary<int, List<string>>();
    PersonAdapter adapter;
    private static int MY_PERMISSIONS_REQUEST_READ_EXTERNAL_STORAGE = 1;
    protected override void OnCreate(Bundle savedInstanceState)
    {
        base.OnCreate(savedInstanceState);
        SetContentView(Resource.Layout.activity_main);
        persons.Add(new Person(0,"Safa", Resource.Drawable.person));
        persons.Add(new Person(1,"Melis", Resource.Drawable.person));
        persons.Add(new Person(2,"Orkun", Resource.Drawable.person));
        messages[0] = new List<string>();
        messages[1] = new List<string>();
        messages[2] = new List<string>();
        messages[0].Add("Naber?");
        messages[0].Add("Nasılsın?");
        messages[1].Add("Nerdesin?");
        messages[1].Add("Saat Kaç?");
        messages[2].Add("Buluşalım mı?");
        messages[2].Add("Kaçta?");
        ListView listView = (ListView)FindViewById(Resource.Id.listView);

        adapter = new PersonAdapter(this,persons);

        listView.Adapter = adapter;



        listView.ItemClick += (object sender, ItemClickEventArgs e) =>
        {
            Person person = persons[e.Position];
            var intent = new Intent(this, typeof(ChatActivity));
            intent.PutExtra("name", person.Name);
            intent.PutExtra("id", person.Id);
            this.StartActivity(intent);
        };



        FloatingActionButton fab = (FloatingActionButton)FindViewById(Resource.Id.fab);

        fab.Click += delegate
        {
            var intent = new Intent(this, typeof(AddContactActivity));
            this.StartActivity(intent);
        };

        if(Intent.GetStringExtra("person") != null)
        {
            Person newPerson = JsonConvert.DeserializeObject<Person>                                                 (Intent.GetStringExtra("person"));
            persons.Add(newPerson);
            messages.Add(newPerson.Id, new List<string>());
            adapter.NotifyDataSetChanged();
        }

    }
}
}

AddContactActivity：

public class AddContactActivity : Activity
{
    private ImageView imageView;
    private Button loadButton;
    private Button addButton;
    private EditText nameEditText, surnameEditText;
    private int index;
    private string filename;
    public static int SELECT_IMAGE = 1001;
    Drawable drawable;
    protected override void OnCreate(Bundle savedInstanceState)
    {
        base.OnCreate(savedInstanceState);
        SetContentView(Resource.Layout.activity_addContact);
        imageView = FindViewById<ImageView>(Resource.Id.load_image_imageView);
        loadButton = FindViewById<Button>(Resource.Id.load_image_button);
        addButton = FindViewById<Button>(Resource.Id.add_contact_button);
        nameEditText = FindViewById<EditText>(Resource.Id.name_editText);
        surnameEditText = FindViewById<EditText>(Resource.Id.surname_editText);
        loadButton.Click += loadButtonClicked;
        addButton.Click += addContactButtonClicked;

    }

    private void addContactButtonClicked(object sender, EventArgs e)
    {
        index = MainActivity.messages.Count;
        Console.WriteLine(index);
        Person newPerson = new Person(index, nameEditText.Text + " " + surnameEditText.Text, drawable.GetHashCode());
        Intent intent = new Intent(this, typeof(MainActivity));
        intent.PutExtra("person", JsonConvert.SerializeObject(newPerson));
        StartActivity(intent);
    }

    private void loadButtonClicked(object sender, EventArgs e)
    {
        if (ContextCompat.CheckSelfPermission(this, Manifest.Permission.ReadExternalStorage) == (int)Permission.Granted)
        {
        Intent = new Intent();
        Intent.SetType("image/*");
        Intent.SetAction(Intent.ActionGetContent);
        StartActivityForResult(Intent.CreateChooser(Intent, "Select Picture"), SELECT_IMAGE);
        }
        else
        {
            ActivityCompat.RequestPermissions(this, new String[] { Manifest.Permission.ReadExternalStorage }, 12);
        }
    }

    protected override void OnActivityResult(int requestCode, Result resultCode, Intent data)
    {
        if ((requestCode == SELECT_IMAGE) && (resultCode == Result.Ok) && (data != null))
        {
                Android.Net.Uri uri = data.Data;
                Bitmap bitmap = MediaStore.Images.Media.GetBitmap(ContentResolver, uri);
                imageView.SetImageBitmap(bitmap);
        }
        else
        {
            Toast.MakeText(this.ApplicationContext, "You haven't picked an image", ToastLength.Short).Show();
        }
    }

    public override void OnRequestPermissionsResult(int requestCode, string[] permissions, Permission[] grantResults)
    {
        if (requestCode == 12)
        {
            if ((grantResults.Length == 1) && (grantResults[0] == Permission.Granted))
            {
                Intent = new Intent();
                Intent.SetType("image/*");
                Intent.SetAction(Intent.ActionGetContent);
                StartActivityForResult(Intent.CreateChooser(Intent, "Select Picture"), SELECT_IMAGE);
            }
        }
        else
        {
            base.OnRequestPermissionsResult(requestCode, permissions, grantResults);
        }
    }

Answer 1

您是否想获得像这样的GIF结果？

根据您的代码，需要执行一些服务器步骤才能实现它。

首先，我们应该使用将位图转换为Base64字符串来实现它，我们可以创建一个MyUtils.cs

        public class MyUtils
    {
        public static string ConvertBitMapToString(Bitmap bitmap)
        {

            byte[] bitmapData;
            using (MemoryStream stream = new MemoryStream())
            {
                bitmap.Compress(Android.Graphics.Bitmap.CompressFormat.Jpeg, 50, stream);
                bitmapData = stream.ToArray();
            }

            string ImageBase64 = Convert.ToBase64String(bitmapData);

            return ImageBase64;
        }

        public static Bitmap ConvertStringToBitmap(string mystr)
        {
            byte[] decodedString = Base64.Decode(mystr, Base64.Default);
            Bitmap decodedByte = BitmapFactory.DecodeByteArray(decodedString, 0, decodedString.Length);

            return decodedByte;
        }
    }

然后我们应将ImageId的类型更改为string，如下面的代码。

    public string ImageId   // property
    {
        get { return imageId; }   // get method
        set { imageId = value; }  // set method
    }

这里是我的演示，您可以下载并参考它。