java - 安卓图片缓存

Question

我有一个动态 View Flipper，它使用 250kb 的图像创建 View 。总 View 为 60。我收到内存不足错误。我将图像存储在可绘制文件夹中。我有一个延迟加载程序的示例代码，但它是从 url 加载的。我想更改功能以从 dawable 文件夹而不是远程 url 中获取。这是我的代码。任何人都可以帮忙吗？

private Bitmap getBitmap(String url)
{
    File f=fileCache.getFile(url);

    //from SD cache
    //CHECK : if trying to decode file which not exist in cache return null
    Bitmap b = decodeFile(f);
    if(b!=null)
        return b;

    // Download image file from web
    try {

        Bitmap bitmap=null;
        URL imageUrl = new URL(url);
        HttpURLConnection conn = (HttpURLConnection)imageUrl.openConnection();
        conn.setConnectTimeout(30000);
        conn.setReadTimeout(30000);
        conn.setInstanceFollowRedirects(true);
        InputStream is=conn.getInputStream();


        // Constructs a new FileOutputStream that writes to file
        // if file not exist then it will create file
        OutputStream os = new FileOutputStream(f);

        // See Utils class CopyStream method
        // It will each pixel from input stream and
        // write pixels to output stream (file)
        Utils.CopyStream(is, os);

        os.close();
        conn.disconnect();

        //Now file created and going to resize file with defined height
        // Decodes image and scales it to reduce memory consumption
        bitmap = decodeFile(f);

        return bitmap;

    } catch (Throwable ex){
        ex.printStackTrace();
        if(ex instanceof OutOfMemoryError)
            memoryCache.clear();
        return null;
    }


}
//Decodes image and scales it to reduce memory consumption
private Bitmap decodeFile(File f){

    try {

        //Decode image size
        BitmapFactory.Options o = new BitmapFactory.Options();
        o.inJustDecodeBounds = true;
        FileInputStream stream1=new FileInputStream(f);
        BitmapFactory.decodeStream(stream1,null,o);
        stream1.close();

        //Find the correct scale value. It should be the power of 2.

        // Set width/height of recreated image
        final int REQUIRED_SIZE=85;

        int width_tmp=o.outWidth, height_tmp=o.outHeight;
        int scale=1;
        while(true){
            if(width_tmp/2 < REQUIRED_SIZE || height_tmp/2 < REQUIRED_SIZE)
                break;
            width_tmp/=2;
            height_tmp/=2;
            scale*=2;
        }

        //decode with current scale values
        BitmapFactory.Options o2 = new BitmapFactory.Options();
        o2.inSampleSize=scale;
        FileInputStream stream2=new FileInputStream(f);
        Bitmap bitmap=BitmapFactory.decodeStream(stream2, null, o2);
        stream2.close();
        return bitmap;

    } catch (FileNotFoundException e) {
    }
    catch (IOException e) {
        e.printStackTrace();
    }
    return null;
}

Answer 1

你可以简单地使用 Picasso 库来处理这个，它会为你做一切

Picasso.with(context).load(R.drawable.drawableName).into(imageView);

在你的适配器中:

@Override
    public View getView(int position, View convertView, ViewGroup parent) {
        ViewHolder holder;

        if (convertView == null) {

            holder = new ViewHolder();
            convertView = inflater.inflate(R.layout.list_item, parent, false);
            holder.imageView = (ImageView) convertView.findViewById(R.id.imageView);

            convertView.setTag(holder);
        } else {
            holder = (ViewHolder) convertView.getTag();
        }
        Picasso.with(context).load(R.drawable.drawableName).into(imageView);
        return convertView;
    }

    class ViewHolder {
        ImageView imageView;
    }

链接:https://github.com/square/picasso

或者如果你还是不喜欢用 Picasso，让我们评论，我会分享一些类来修改图像，保存到缓存并加载，但是它太长了......