android中判断某个应用是否存在

public boolean checkApk(String packageName) { 
    if (packageName == null || "".equals(packageName)) 
        return false; 
    try { 
        ApplicationInfo info = getPackageManager().getApplicationInfo( 
                packageName, PackageManager.GET_UNINSTALLED_PACKAGES); 
        return true; 
    } catch (NameNotFoundException e) { 
        return false; 
    } 
}