带有图像的xamarin android ListView

Question

Im tring to load data from database and display on a ListView. The list view contains 2 textview and 1 image view. Im using SQlite.net. Where is my databse:

Database

public class contacts
{
    [PrimaryKey, AutoIncrementAttribute, Column("id")]
    public int id {get; set;}
    public string name {get; set;}
    public string number { get; set; }
    public byte[] photo{ get; set; }
}

And where is my function to fill the listview:

private void refreshListView()
    {           
        var db = new SQLiteConnection (MainActivity._DatabaseConnectString);

        MatrixCursor mMatrixCursor = new MatrixCursor (new String[]{ "_id", "name", "number", "photo" });

        SimpleCursorAdapter adap;

        adap = new SimpleCursorAdapter (
            this,
            Resource.Layout.lv_layout,
            null,
            new String[]{ "name", "number", "photo" },
            new int[]{ Resource.Id.tv_name, Resource.Id.tv_number, Resource.Id.iv_photo }, 0);

        IEnumerable<contacts> table = db.Query<contacts> ("select * from contacts");
        foreach (var contact in table) {
            mMatrixCursor.AddRow (new Java.Lang.Object[] {contact.id,
                contact.name, contact.number, BitmapFactory.DecodeByteArray (contact.photo, 0, contact.photo.Length)
            });
        }

        lview.Adapter = adap;
        adap.SwapCursor (mMatrixCursor);
    }

The only problem is the image dont show and I have this error from the output:

[BitmapFactory] Unable to decode stream: java.io.FileNotFoundException: /android.graphics.Bitmap@42087da0: open failed: ENOENT (No such file or directory)
[System.out] resolveUri failed on bad bitmap uri: android.graphics.Bitmap@42087da0

I already done this application with java for android and I fix that problem with the this code but I dont know how to "translate" the code from java to c#.

Where is the java code below the adap:

adap.setViewBinder(new SimpleCursorAdapter.ViewBinder() {
        @Override
        public boolean setViewValue(View view, Cursor cursor, int i) {
            if (view.getId() == R.id.iv_photo) {
                byte[] Blobdata = cursor.getBlob(i);

                Bitmap bitmap = Bitmap.createScaledBitmap(BitmapFactory.decodeByteArray(
                        Blobdata, 0, Blobdata.length), 150, 150, false);

                ((ImageView) view).setImageBitmap(bitmap);
                return true;
            } else {
                return false;
            }
        }
    });

Somebody can help me "translate" this code to c#? or use another code. Thanks from the help and sorry my english.

EDITED 2

Ok where is the code translated to c#

class ViewBinder : Java.Lang.Object, SimpleCursorAdapter.IViewBinder
    {     
        public bool SetViewValue (View view, Android.Database.ICursor cursor, int i)
        {
            if (view.Id == Resource.Id.iv_photo) {

                byte[] Blobdata = cursor.GetBlob (i);

                Bitmap bitmap = Bitmap.CreateScaledBitmap (BitmapFactory.DecodeByteArray (
                                    Blobdata, 0, Blobdata.Length), 150, 150, false);

                ((ImageView)view).SetImageBitmap (bitmap);
                return true;
            } else {
                return false;
            }
        }     
    }

But now I got an error in this line:

byte[] Blobdata = cursor.GetBlob (i);

Error:

android.graphics.Bitmap cannot be cast to byte[]

I think im getting this error becouse in my database im not using Blob but byte array. Somebody know how I can retrive byte array from database or how i can use Blob data type?

Answer 1

You can store a byte-array in a BLOB.

This is how I fetch it:

using (SqliteDataReader reader = command.ExecuteReader())
{
    while (reader.Read())
    {
        images.Add(new Image((byte[])reader["Image"]));
    }
}

I can then use my Image property ImageByteArray to convert it to a Bitmap, similar to the way you did.

Bitmap image = BitmapFactory.DecodeByteArray(data, 0, barray.Length);

The Bitmap is then ready to show in an ImageView .

imageView.SetImageBitmap(image);

As you can see, our methods are very much alike. So to me it seems cursor.GetBlob (i) returns something unexpected.

public abstract byte[] getBlob (int columnIndex)

Added in API level 1 Returns the value of the requested column as a byte array.

The result and whether this method throws an exception when the column value is null or the column type is not a blob type is implementation-defined.

Parameters: columnIndex the zero-based index of the target column.

Returns: the value of that column as a byte array.

( http://developer.android.com/reference/android/database/Cursor.html#getBlob(int) )

According to the description from the method, it seems your column does not hold a BLOB/byte-array.

Use var Blobdata = cursor.GetBlob (i); to find out what is in it, and adjust accordingly.