Question

我想从listview项目中的sdcard获取图像我能够显示图像，但我想缓存该图像，以便我有流畅的滚动任何人都可以告诉我如何从SD卡缓存图像我得到了代码，但它显示图片来自drawable但我想从sdcard

import java.lang.ref.WeakReference;
import java.util.ArrayList;

import android.content.Context;
import android.content.res.Resources;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.drawable.BitmapDrawable;
import android.graphics.drawable.Drawable;
import android.os.AsyncTask;
import android.util.LruCache;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.GridLayout.LayoutParams;
import android.widget.GridView;
import android.widget.ImageView;

public class ListAdapter extends BaseAdapter {

    Context context;
    ArrayList<String> items;
    private LruCache<String, Bitmap> mMemoryCache;

    public ListAdapter(Context context, ArrayList<String> items) {
        this.context = context;
        this.items = items;

        // Get memory class of this device, exceeding this amount will throw an
        // OutOfMemory exception.
        final int maxMemory = (int) (Runtime.getRuntime().maxMemory() / 1024);

        // Use 1/8th of the available memory for this memory cache.
        final int cacheSize = maxMemory / 8;

        mMemoryCache = new LruCache<String, Bitmap>(cacheSize) {

            protected int sizeOf(String key, Bitmap bitmap) {
                // The cache size will be measured in bytes rather than number
                // of items.
                return bitmap.getByteCount();
            }

        };
    }

    @Override
    public int getCount() {
        return items.size();
    }

    @Override
    public Object getItem(int arg0) {
        return items.get(arg0);
    }

    @Override
    public long getItemId(int arg0) {
        return arg0;
    }

    @Override
    public View getView(int arg0, View convertView, ViewGroup arg2) {
        ImageView img = null;

        if (convertView == null) {
            img = new ImageView(context);
            img.setScaleType(ImageView.ScaleType.CENTER_CROP);
            img.setLayoutParams(new GridView.LayoutParams(
                    LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT));
        } else {
            img = (ImageView) convertView;
        }

        int resId = context.getResources().getIdentifier(items.get(arg0),
                "drawable", context.getPackageName());

        loadBitmap(resId, img);

        return img;
    }

    public void loadBitmap(int resId, ImageView imageView) {
        if (cancelPotentialWork(resId, imageView)) {
            final BitmapWorkerTask task = new BitmapWorkerTask(imageView);
            imageView.setBackgroundResource(R.drawable.empty_photo);
            task.execute(resId);
        }
    }

    static class AsyncDrawable extends BitmapDrawable {
        private final WeakReference<BitmapWorkerTask> bitmapWorkerTaskReference;

        public AsyncDrawable(Resources res, Bitmap bitmap,
                BitmapWorkerTask bitmapWorkerTask) {
            super(res, bitmap);
            bitmapWorkerTaskReference = new WeakReference<BitmapWorkerTask>(
                    bitmapWorkerTask);
        }

        public BitmapWorkerTask getBitmapWorkerTask() {
            return bitmapWorkerTaskReference.get();
        }
    }

    public static boolean cancelPotentialWork(int data, ImageView imageView) {
        final BitmapWorkerTask bitmapWorkerTask = getBitmapWorkerTask(imageView);

        if (bitmapWorkerTask != null) {
            final int bitmapData = bitmapWorkerTask.data;
            if (bitmapData != data) {
                // Cancel previous task
                bitmapWorkerTask.cancel(true);
            } else {
                // The same work is already in progress
                return false;
            }
        }
        // No task associated with the ImageView, or an existing task was
        // cancelled
        return true;
    }

    private static BitmapWorkerTask getBitmapWorkerTask(ImageView imageView) {
        if (imageView != null) {
            final Drawable drawable = imageView.getDrawable();
            if (drawable instanceof AsyncDrawable) {
                final AsyncDrawable asyncDrawable = (AsyncDrawable) drawable;
                return asyncDrawable.getBitmapWorkerTask();
            }
        }
        return null;
    }

    public void addBitmapToMemoryCache(String key, Bitmap bitmap) {
        if (getBitmapFromMemCache(key) == null) {
            mMemoryCache.put(key, bitmap);
        }
    }

    public Bitmap getBitmapFromMemCache(String key) {
        return (Bitmap) mMemoryCache.get(key);
    }

    class BitmapWorkerTask extends AsyncTask<Integer, Void, Bitmap> {
        public int data = 0;
        private final WeakReference<ImageView> imageViewReference;

        public BitmapWorkerTask(ImageView imageView) {
            // Use a WeakReference to ensure the ImageView can be garbage
            // collected
            imageViewReference = new WeakReference<ImageView>(imageView);
        }

        // Decode image in background.
        @Override
        protected Bitmap doInBackground(Integer... params) {
            data = params[0];
            final Bitmap bitmap = decodeSampledBitmapFromResource(
                    context.getResources(), data, 100, 100);
            addBitmapToMemoryCache(String.valueOf(params[0]), bitmap);
            return bitmap;
        }

        // Once complete, see if ImageView is still around and set bitmap.
        @Override
        protected void onPostExecute(Bitmap bitmap) {
            if (imageViewReference != null && bitmap != null) {
                final ImageView imageView = imageViewReference.get();
                if (imageView != null) {
                    imageView.setImageBitmap(bitmap);
                }
            }
        }
    }

    public static Bitmap decodeSampledBitmapFromResource(Resources res,
            int resId, int reqWidth, int reqHeight) {

        // First decode with inJustDecodeBounds=true to check dimensions
        final BitmapFactory.Options options = new BitmapFactory.Options();
        options.inJustDecodeBounds = true;
        BitmapFactory.decodeResource(res, resId, options);

        // Calculate inSampleSize
        options.inSampleSize = calculateInSampleSize(options, reqWidth,
                reqHeight);

        // Decode bitmap with inSampleSize set
        options.inJustDecodeBounds = false;
        return BitmapFactory.decodeResource(res, resId, options);
    }

    public static int calculateInSampleSize(BitmapFactory.Options options,
            int reqWidth, int reqHeight) {
        // Raw height and width of image
        final int height = options.outHeight;
        final int width = options.outWidth;
        int inSampleSize = 1;

        if (height > reqHeight || width > reqWidth) {

            // Calculate ratios of height and width to requested height and
            // width
            final int heightRatio = Math.round((float) height
                    / (float) reqHeight);
            final int widthRatio = Math.round((float) width / (float) reqWidth);

            // Choose the smallest ratio as inSampleSize value, this will
            // guarantee
            // a final image with both dimensions larger than or equal to the
            // requested height and width.
            inSampleSize = heightRatio < widthRatio ? heightRatio : widthRatio;
        }

        return inSampleSize;
    }

}

Answer 1

我认为你必须使用AQuery。从here下载AQuery jar文件。将其添加到您的构建路径中，然后将其显示在您要显示图像的位置，只需将其显示如下：

AQuery aQuery=new AQuery(this);
File file = new File(YOUR IMAGE PATH);        
aq.id(R.id.avatar).image(file, true,true); // that both true means you caching your images.

从sdcard安装android缓存图片

1 个答案: