android 4.4以下loadIocn nullpointerException问题

之前一直没注意，今天有同学跟我说在oppo n1手机上获取apk安装包时会崩溃，看到的崩溃信息是

java.lang.NullPointerException    at android.app.ActivityThread$ResourcesKey.(ActivityThread.java:2200)    at android.app.ActivityThread.getTopLevelResources(ActivityThread.java:187)    at android.app.ActivityThread.getTopLevelResources(ActivityThread.java:246)    at android.app.ContextImpl$ApplicationPackageManager.getResourcesForApplication(ContextImpl.java:2188)    at android.app.ContextImpl$ApplicationPackageManager.getDrawable(ContextImpl.java:2114)    at android.content.pm.PackageItemInfo.loadIcon(PackageItemInfo.java:131)    at android.app.ContextImpl$ApplicationPackageManager.getApplicationIcon(ContextImpl.java:2169)    at com.metago.astro.IconManager.loadPackageIcon(IconManager.java:330)

从异常信息可以看出是在ResourcesKey的构造时崩溃的。找到4.2的该类定义

    ResourcesKey(String resDir, int displayId, Configuration overrideConfiguration, float scale) {1516            mResDir = resDir;1517            mDisplayId = displayId;1518            if (overrideConfiguration != null) {1519                if (Configuration.EMPTY.equals(overrideConfiguration)) {1520                    overrideConfiguration = null;1521                }1522            }1523            mOverrideConfiguration = overrideConfiguration;1524            mScale = scale;1525            int hash = 17;1526            hash = 31 * hash + mResDir.hashCode();1527            hash = 31 * hash + mDisplayId;1528            hash = 31 * hash + (mOverrideConfiguration != null1529                    ? mOverrideConfiguration.hashCode() : 0);1530            hash = 31 * hash + Float.floatToIntBits(mScale);1531            mHash = hash;

可以看到类在构造时没有对resDir进行校验，在第1526行引用时就可能报空指针问题
而我一直使用的note3并未出现此问题，于是再看到4.4上这个类的定义

31    public More ...ResourcesKey(String resDir, int displayId, Configuration overrideConfiguration,32            float scale, IBinder token) {33        mResDir = resDir;34        mDisplayId = displayId;35        if (overrideConfiguration != null) {36            mOverrideConfiguration.setTo(overrideConfiguration);37        }38        mScale = scale;39        mToken = token;4041        int hash = 17;42        hash = 31 * hash + (mResDir == null ? 0 : mResDir.hashCode());43        hash = 31 * hash + mDisplayId;44        hash = 31 * hash + (mOverrideConfiguration != null45                ? mOverrideConfiguration.hashCode() : 0);46        hash = 31 * hash + Float.floatToIntBits(mScale);47        mHash = hash;48    }

看到4.4中的42行在引用时进行了判空，所以并没有崩溃。这种情况下获取到的icon都是默认的，也就是安卓那个小绿机器人。
解决这个问题的办法是在获取了apk安装包的applicationInfo后，

applicationInfo.sourceDir = "apkpath";applicationInfo.publicSourceDir = "apkpath";

把这apk的路径赋予这两个值任意之一就行，因为从activityThread.java可以看到，resDir取的就是sourceDir和publicSourceDir之一。

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