有什么理由从资源preloading可绘制？ [英] Is there any reason to preloading drawables from resources?

问题描述

难道Android的维护应用程序绘制资源，内存缓存和重新使用它们，或者它是一个很好的做法，preLOAD可动态地分配给不同的部件全部可绘制？

例如：

 公共静态最终诠释[]设置= {
        R.drawable.set0，R.drawable.set1，R.drawable.set2，
        R.drawable.set3，R.drawable.set4，R.drawable.set5，R.drawable.set6，
        R.drawable.set7，R.drawable.set8，R.drawable.set9，R.drawable.set10};
市民可绘制[]套;

无效的init（）{
    负载（套，套）;
}

公共无效负载（可绘制[] D，INT [] IDS）{
    的for（int i = 0; I＆LT; ids.length;我++）{
        如果（IDS [我] == 0）
            D [I] =无效;
        其他
            。D [i] = context.getResources（）getDrawable（IDS [I]）;
    }
}
 

解决方案

这闻起来像一个不必要的pre-优化。然而，Android的做缓存可绘制，所以你不必pre-加载它们。从的ApplicationContext

相关code

  / *包* /可绘制loadDrawable（的TypedValue值，INT ID）
            抛出NotFoundException {
        。
        。
        。

        最终的长键=（（（长）value.assetCookie）＆LT;＆LT; 32）| value.data;
        绘制对象博士= getCachedDrawable（密钥）;

        如果（DR！= NULL）{
            返回博士;
        }

        。
        。
        。

        如果（DR！= NULL）{
            dr.setChangingConfigurations（value.changingConfigurations）;
            CS = dr.getConstantState（）;
            如果（CS！= NULL）{
                如果（M preloading）{
                    US preloadedDrawables.put（键，CS）;
                } 其他 {
                    同步（mTmpValue）{
                        //Log.i(TAG，保存缓存绘制@＃+
                        // Integer.toHexString（key.intValue（））
                        // +中的+本+：+ CS）;
                        mDrawableCache.put（重点，新的WeakReference＆LT; D​​rawable.ConstantState＆GT;（CS））;
                    }
                }
            }
        }

        返回博士;
    }

    私人绘制对象getCachedDrawable（长键）{
        同步（mTmpValue）{
            WeakReference的＆LT; D​​rawable.ConstantState＆GT; WR = mDrawableCache.get（密钥）;
            如果（WR！= NULL）{//我们有钥匙
                Drawable.ConstantState条目= wr.get（）;
                如果（入门！= NULL）{
                    //Log.i(TAG，返回缓存绘制@＃+
                    // Integer.toHexString（（（整数）键）.intValue（））
                    // +在+本+：+条目）;
                    返回entry.newDrawable（本）;
                }
                其他{//我们的项目已被清除
                    mDrawableCache.delete（键）;
                }
            }
        }
        返回null;
    }
 

Does Android maintain a memory cache of application drawable resources and reuse them, or it is a good practice to preload all drawables that may be assigned dynamically to different widgets?

For instance:

public static final int[] SETS = {
        R.drawable.set0, R.drawable.set1, R.drawable.set2,
        R.drawable.set3, R.drawable.set4, R.drawable.set5, R.drawable.set6,
        R.drawable.set7, R.drawable.set8, R.drawable.set9, R.drawable.set10};
public Drawable[] sets;

void init() {
    load(sets, SETS);
}

public void load(Drawable[] d, int[] ids) {
    for (int i = 0; i < ids.length; i++) {
        if (ids[i] == 0)
            d[i] = null;
        else
            d[i] = context.getResources().getDrawable(ids[i]);
    }
}

解决方案

This smells like an unnecessary pre-optimization. However, android does cache drawables so you don't have to pre-load them. Relevant code from ApplicationContext

  /*package*/ Drawable loadDrawable(TypedValue value, int id)
            throws NotFoundException {
        .
        .
        .

        final long key = (((long) value.assetCookie) << 32) | value.data;
        Drawable dr = getCachedDrawable(key);

        if (dr != null) {
            return dr;
        }

        .
        .
        .

        if (dr != null) {
            dr.setChangingConfigurations(value.changingConfigurations);
            cs = dr.getConstantState();
            if (cs != null) {
                if (mPreloading) {
                    sPreloadedDrawables.put(key, cs);
                } else {
                    synchronized (mTmpValue) {
                        //Log.i(TAG, "Saving cached drawable @ #" +
                        //        Integer.toHexString(key.intValue())
                        //        + " in " + this + ": " + cs);
                        mDrawableCache.put(key, new WeakReference<Drawable.ConstantState>(cs));
                    }
                }
            }
        }

        return dr;
    }

    private Drawable getCachedDrawable(long key) {
        synchronized (mTmpValue) {
            WeakReference<Drawable.ConstantState> wr = mDrawableCache.get(key);
            if (wr != null) {   // we have the key
                Drawable.ConstantState entry = wr.get();
                if (entry != null) {
                    //Log.i(TAG, "Returning cached drawable @ #" +
                    //        Integer.toHexString(((Integer)key).intValue())
                    //        + " in " + this + ": " + entry);
                    return entry.newDrawable(this);
                }
                else {  // our entry has been purged
                    mDrawableCache.delete(key);
                }
            }
        }
        return null;
    }

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