library/src/main/java/com/bumptech/glide/load/engine/prefill/BitmapPreFiller.java

package com.bumptech.glide.load.engine.prefill;

import android.graphics.Bitmap;
import android.os.Handler;
import android.os.Looper;

import com.bumptech.glide.load.DecodeFormat;
import com.bumptech.glide.load.engine.bitmap_recycle.BitmapPool;
import com.bumptech.glide.load.engine.cache.MemoryCache;
import com.bumptech.glide.util.Util;

import java.util.HashMap;
import java.util.Map;

/**
 * A class for pre-filling {@link android.graphics.Bitmap Bitmaps} in a
 * {@link com.bumptech.glide.load.engine.bitmap_recycle.BitmapPool}.
 */
public final class BitmapPreFiller {

    private final MemoryCache memoryCache;
    private final BitmapPool bitmapPool;
    private final DecodeFormat defaultFormat;
    private final Handler handler = new Handler(Looper.getMainLooper());

    private BitmapPreFillRunner current;

    public BitmapPreFiller(MemoryCache memoryCache, BitmapPool bitmapPool, DecodeFormat defaultFormat) {
        this.memoryCache = memoryCache;
        this.bitmapPool = bitmapPool;
        this.defaultFormat = defaultFormat;
    }

    public void preFill(PreFillType.Builder... bitmapAttributeBuilders) {
        if (current != null) {
            current.cancel();
        }

        PreFillType[] bitmapAttributes = new PreFillType[bitmapAttributeBuilders.length];
        for (int i = 0; i < bitmapAttributeBuilders.length; i++) {
            PreFillType.Builder builder = bitmapAttributeBuilders[i];
            if (builder.getConfig() == null) {
                builder.setConfig(defaultFormat == DecodeFormat.ALWAYS_ARGB_8888
                        ? Bitmap.Config.ARGB_8888 : Bitmap.Config.RGB_565);
            }
            bitmapAttributes[i] = builder.build();
        }

        PreFillQueue allocationOrder = generateAllocationOrder(bitmapAttributes);
        current = new BitmapPreFillRunner(bitmapPool, memoryCache, allocationOrder);
        handler.post(current);
    }

    // Visible for testing.
    PreFillQueue generateAllocationOrder(PreFillType[] preFillSizes) {
        final int maxSize = memoryCache.getMaxSize() - memoryCache.getCurrentSize() + bitmapPool.getMaxSize();

        int totalWeight = 0;
        for (PreFillType size : preFillSizes) {
            totalWeight += size.getWeight();
        }

        final float bytesPerWeight = maxSize / (float) totalWeight;

        Map<PreFillType, Integer> attributeToCount = new HashMap<PreFillType, Integer>();
        for (PreFillType size : preFillSizes) {
            int bytesForSize = Math.round(bytesPerWeight * size.getWeight());
            int bytesPerBitmap = getSizeInBytes(size);
            int bitmapsForSize = bytesForSize / bytesPerBitmap;
            attributeToCount.put(size, bitmapsForSize);
        }

        return new PreFillQueue(attributeToCount);
    }

    private static int getSizeInBytes(PreFillType size) {
        return Util.getBitmapByteSize(size.getWidth(), size.getHeight(), size.getConfig());
    }
}