获取静态apk包(未安装)的packagename

frameworks\base\services\java\com\android\server\pm\PackageManagerService.java
installPackageWithVerificationAndEncryption(...)方法中 获取静态apk包(未安装)的packagename.....
具体方法如下：
final String archiveFilePath = packageURI.getPath();
PackageParser pp = new PackageParser(archiveFilePath);
File sourceFile = new File(archiveFilePath);
DisplayMetrics metrics = new DisplayMetrics();
metrics.setToDefaults();
PackageParser.Package pkg = pp.parsePackage(sourceFile,
archiveFilePath, metrics, 0); //此时获取的pkg也为null
if(pkg!=null){
Log.i("0410","pkg is not null");
}else{
Log.i("0410","pkg is null");
}

可是获取的pkg为null 请高手指点指点.....