图像适配器+图库成像循环

时间：2013-07-23 03:08:38

标签： java android android-adapter

我正在处理其中一个应用程序的问题。当我按下图库按钮并开始加载时，它会显示所有图片，但除了一次按下之外它在网格中的相同照片，它与gridview中显示的图像不同。下面是我正在使用的代码以及一些照片：

以下是图像适配器中的代码：

public class ImageAdapter extends BaseAdapter {
    private Context mContext;

    public Integer[] Tattoos = {
        R.drawable.tattoo1, R.drawable.tattoo2,
        R.drawable.tattoo3, R.drawable.tattoo4,
        R.drawable.tattoo5, R.drawable.tattoo6,
        R.drawable.tattoo7, R.drawable.tattoo8,
        R.drawable.tattoo9, R.drawable.tattoo10, 
        R.drawable.tattoo11, R.drawable.tattoo12,
        R.drawable.tattoo13, R.drawable.tattoo14,
        R.drawable.tattoo15, R.drawable.tattoo16,
        R.drawable.tattoo17, R.drawable.tattoo18,
        R.drawable.tattoo19, R.drawable.tattoo20, 
        R.drawable.tattoo21, R.drawable.tattoo22,
        R.drawable.tattoo23, R.drawable.tattoo24,
        R.drawable.tattoo25, R.drawable.tattoo26,
        R.drawable.tattoo27, R.drawable.tattoo28,
        R.drawable.tattoo29, R.drawable.tattoo30, 
        R.drawable.tattoo31, R.drawable.tattoo32,
        R.drawable.tattoo33, R.drawable.tattoo34,
        R.drawable.tattoo35, R.drawable.tattoo36,
        R.drawable.tattoo37, R.drawable.tattoo38,
        R.drawable.tattoo39, R.drawable.tattoo40, 
        R.drawable.tattoo41, R.drawable.tattoo42,
        R.drawable.tattoo43, R.drawable.tattoo44,
        R.drawable.tattoo45, R.drawable.tattoo46,
        R.drawable.tattoo47, R.drawable.tattoo48,
        R.drawable.tattoo49, R.drawable.tattoo50, 
        R.drawable.tattoo51, R.drawable.tattoo52,
        R.drawable.tattoo53, R.drawable.tattoo54,
        R.drawable.tattoo55, R.drawable.tattoo56,
        R.drawable.tattoo57, R.drawable.tattoo58,
        R.drawable.tattoo59, R.drawable.tattoo60, 
        R.drawable.tattoo61, R.drawable.tattoo62,
        R.drawable.tattoo63, R.drawable.tattoo64,
        R.drawable.tattoo65, R.drawable.tattoo66,
        R.drawable.tattoo67, R.drawable.tattoo68,
        R.drawable.tattoo69, R.drawable.tattoo70, 
        R.drawable.tattoo71, R.drawable.tattoo72,
        R.drawable.tattoo73, R.drawable.tattoo74,
        R.drawable.tattoo75, R.drawable.tattoo76,
        R.drawable.tattoo77, R.drawable.tattoo78,
        R.drawable.tattoo79, R.drawable.tattoo80,
        R.drawable.tattoo81, R.drawable.tattoo82
    };

    // Constructor
    public ImageAdapter(Context c){
        mContext = c;
    }

    public int getCount() {
        return Tattoos.length;
    }

    public Object getItem(int position) {
        return Tattoos[position];
    }

    public long getItemId(int position) {
        return 0;
    }

    public View getView(int position, View convertView, ViewGroup parent) {
        //This actually is a bad solution, because every time convertView is reused, you will still initialize new ImageView, which is wrong
        //ImageView imageView = new ImageView(this.mContext);
        //new BitmapWorkerTask(imageView).execute(Tattoos[position]);
        //return imageView;

        //Better solution
        ImageView imageView = null;

        if (convertView == null) {
            imageView = new ImageView(this.mContext);
            new BitmapWorkerTask(imageView).execute(Tattoos[position]);
            //create new ImageView if it is not present and populate it with some image
        } else {
            imageView = (ImageView) convertView;
            //re-use ImageView that already exists in memory
        }

        return imageView;
    }


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

        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];
            return decodeSampledBitmapFromResource(ImageAdapter.this.mContext.getResources(), data, 100, 100);
        }

        // 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);
                    imageView.setScaleType(ImageView.ScaleType.CENTER_CROP);
                    imageView.setLayoutParams(new GridView.LayoutParams(100, 70));
                }
            }
        }
    }

    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;
    }
}

任何帮助将不胜感激

1 个答案:

答案 0 :(得分：1)

我不确定'gallery按钮'是什么意思，因为问题中没有触控处理代码。

即便如此，我认为您的适配器的问题在于使用ImageView引用。基本上GridView应管理视图创建和回收，以便重新用于其他项目（然后您将通过convertView获得该视图）。所以，我建议使用如下的位图缓存：

public class ImageAdapter extends BaseAdapter {

    private static final String TAG = "ImageAdapter";

    private Context mContext;

    public static final Integer[] TATTOOS = {
        R.drawable.image001, R.drawable.image002,
        R.drawable.image003, R.drawable.image004,
        R.drawable.image005, R.drawable.image006,
        R.drawable.image007, R.drawable.image008,
        R.drawable.image009, R.drawable.image010,
        R.drawable.image011, R.drawable.image012,
        R.drawable.image013, R.drawable.image014,
        R.drawable.image015, R.drawable.image016,
        R.drawable.image017, R.drawable.image018,
        R.drawable.image019, R.drawable.image020,
        R.drawable.image021, R.drawable.image022,
        R.drawable.image023, R.drawable.image024,
        R.drawable.image025, R.drawable.image026,
        R.drawable.image027, R.drawable.image028,
        R.drawable.image029, R.drawable.image030,
        R.drawable.image031, R.drawable.image032,
        R.drawable.image033, R.drawable.image034,
        R.drawable.image035, R.drawable.image036,
        R.drawable.image037, R.drawable.image038,
        R.drawable.image039, R.drawable.image040,
        R.drawable.image041, R.drawable.image042,
        R.drawable.image043, R.drawable.image044,
        R.drawable.image045, R.drawable.image046,
        R.drawable.image047, R.drawable.image048,
        R.drawable.image049, R.drawable.image050
    };

    private Bitmap mHolder = null;
    private static final int CACHE_SIZE = 30 * 1024 * 1024; // 8 MiB cache
    /** Cache to store all decoded images */
    private LruCache<Integer, Bitmap> mBitmapsCache = new LruCache<Integer, Bitmap>(CACHE_SIZE) {

        @Override
        protected int sizeOf(final Integer key, final Bitmap value) {
            return value.getByteCount();
        }

        @Override
        protected void entryRemoved(final boolean evicted, final Integer key, final Bitmap oldValue, final Bitmap newValue) {
            if (!oldValue.equals(mHolder)) {
                oldValue.recycle();
            }
        }
    };

    // Constructor
    public ImageAdapter(Context c){
        mContext = c;
        mHolder = BitmapFactory.decodeResource(c.getResources(), R.drawable.ic_launcher, null);
    }

    @Override
    public int getCount() {
        return TATTOOS.length;
    }

    @Override
    public Object getItem(int position) {
        return TATTOOS[position];
    }

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

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        //This actually is a bad solution, because every time convertView is reused, you will still initialize new ImageView, which is wrong
        //ImageView imageView = new ImageView(this.mContext);
        //new BitmapWorkerTask(imageView).execute(Tattoos[position]);
        //return imageView;

        //Better solution
        ImageView imageView;

        if (convertView == null) {
            imageView = new ImageView(this.mContext);

            imageView.setScaleType(ImageView.ScaleType.CENTER_CROP);
            imageView.setLayoutParams(new GridView.LayoutParams(300, 300));
        } else {
            imageView = (ImageView) convertView;
            //re-use ImageView that already exists in memory
        }

        final Bitmap itemBitmap = mBitmapsCache.get(TATTOOS[position]);

        if (itemBitmap == null || itemBitmap.isRecycled()) {
            Log.e(TAG, position + " is missed, launch decode for " + TATTOOS[position]);
            imageView.setImageBitmap(mHolder);
            mBitmapsCache.put(TATTOOS[position], mHolder);
            new BitmapWorkerTask(mBitmapsCache, mContext.getResources(), this).execute(TATTOOS[position]);
        } else {
            Log.e(TAG, position + " is here for " + TATTOOS[position]);
            imageView.setImageBitmap(itemBitmap);
        }

        return imageView;
    }

    /** AsyncTask for decoding images from resources */
    static class BitmapWorkerTask extends AsyncTask<Integer, Void, Bitmap> {
        private int data = 0;
        private final LruCache<Integer, Bitmap> mCache;
        private final Resources mRes;
        private final BaseAdapter mAdapter;

        public BitmapWorkerTask(LruCache<Integer, Bitmap> cache, Resources res, BaseAdapter adapter) {
            // nothing to do here
            mCache = cache;
            mRes = res;
            mAdapter = adapter;
        }

        // Decode image in background.
        @Override
        protected Bitmap doInBackground(Integer... params) {
            data = params[0];
            return decodeSampledBitmapFromResource(mRes, data, 300, 300);
        }

        // Once complete, see if ImageView is still around and set bitmap.
        @Override
        protected void onPostExecute(Bitmap bitmap) {
            mCache.put(data, bitmap);
            mAdapter.notifyDataSetChanged();
        }
    }

    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;
        options.outHeight = 300;
        options.outWidth = 300;
        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;
    }
}

我还添加了'holder'位图，用于显示图像加载并避免同一资源的多次解码启动。

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