在Android中的列表视图中显示和滚动大位图时出现异常

Question

I am facing this issue but unable to resolve. My problem goes like this:

• I have a list view. My list row contains an image view and one text view
• I have 20 images each of 12 MB size stored in my SD card
• I have to set these images in imageView of my list view

I am able to do it by following code. This I am doing in getView method of my custom adapter:

public View getView (int position, View convertView, ViewGroup parent) {
    //other stuffs like recycling, view holder etc...
    BitmapFactory.Options opt = new BitmapFactory.Options();
    opt.inSampleSize = 4; // tried with 8,12 too
    Bitmap bitmap = BitmapFactory.decodeFile(imageUri, opt);
    holder.imageView.setImageBitmap(bitmap);
    return convertView;
}

Now this code works fine with small images but plays havoc for image of large size. Application crashes with OutOfMemoryError . If I try to increase inSampleSize to 8 or 12, it works but image quality drastically comes down and image doesn't look original image at all. I tried with imageView.setImageURI(imageUri) also but documentation suggests to use setImageBitmap only.

Now please someone help me to rectify this issue. How can I resolve this without compromising with image quality?

Answer 1

A quick band-aid that might help would be to use:

opt.inPreferredConfig = Bitmap.Config.RGB_565;

That will load your images without an alpha channel, and only using 2 bytes per pixel (rather than 4 bytes with the default ARGB_8888).

Depending on the length of your list, you might have to load/unload your images as they become visible on screen/leave the screen.

Answer 2

Try setting inSampleSize to 2 or 4, and scale width and height down using the Matrix class. But as you said in another answer, this may hit performance.

float desiredWidth = 60; // the width you want your icon/image to be
float scale = desiredWidth/actualWidth // bitmap.getWidth() for actualWidth
// float scale = desiredHeight/actualHeight // If you want to go by a particular height

Matrix matrix = new Matrix();
matrix.setScale(scale, scale);

holder.imageView.setImageBitmap(Bitmap.createBitmap(bitmap, 0, 0, bitmap.getWidth(), bitmap.getHeight(), matrix, false));
bitmap.recycle(); // ish

Second option. Before instantiating the Adapter class, get a Cursor object to thumbnail images and pass the cursor into the constructor of the adapter, making it a class varaible. Use the same cursor on every view row in the ListView.

Uri tUri = MediaStore.Images.Thumbnails.EXTERNAL_CONTENT_URI; // Where thumbnails are stored
String[] columns = { MediaStore.Images.ImageColumns._ID,  MediaStore.Images.ImageColumns.DATE_TAKEN, MediaStore.Images.ImageColumns.DISPLAY_NAME};

Cursor thumbCursor = this.managedQuery(tUri, null, null, null, null); // May want to use more paramaters to filter results
cursor.moveToFirst();

.... instantiate adapter, pass in cursor ....

public View getView (int position, View convertView, ViewGroup parent) {

int columnIndex = cursor.getColumnIndex(MediaStore.Images.Thumbnails.DATA);
String filePath = cursor.getString(columnIndex);
Bitmap bitmap = BitmapFactory.decodeFile(filePath);
holder.imageView.setImageBitmap(bitmap);
cur.moveToNext();
// BitmapDrawable d = new BitmapDrawable(listActivity.getResources(), filePath);
// holder.imageView.setImageDrawable(d);
}

Something like that. I did it in a hurry. Good luck =)

Answer 3

尝试根据图像尺寸计算比例因子，并调用Bitmap.recycle（）来释放分配的内存

Answer 4

First of all, as images are of 12mb(even if they are of only 1mb), you have to scale them and downsize them to the dimensions of your imageview .

while you can also check for outofmemory exception ...

public View getView (int position, View convertView, ViewGroup parent) 
{
//other stuffs like recycling, view holder etc...

    boolean OOME = true;
    int sample = 4;

    while(OOME)
    {
        try
        {
            BitmapFactory.Options opt = new BitmapFactory.Options();
            opt.inSampleSize = sample; // tried with 8,12 too
            Bitmap bitmap = BitmapFactory.decodeFile(imageUri, opt);
            bitmap = bitmap.createScaledBitmap(bitmap,newWidth,newHeight,true);
            holder.imageView.setImageBitmap(bitmap);
            OOME = false;
        }
        catch(OutOfMemoryError e)
        {
            sample *= 2;
        }
    }
    return convertView;
}

I also take assumption, you are doing all the decoding stuff in a background thread to make your listview scroll smooth...

While having many problems with Bitmaps and ListView , this was the best approach i can come with... still I am open for any changes or modifications or enhancments ...