查询APK是否安装

/**
     * 查询系统是否安装packageName的apk
     */
    public static boolean isInstallApk(Context context, String packageName)
    {
    	PackageManager packageManager = context.getPackageManager();
    	java.util.List<PackageInfo> apps = new ArrayList<PackageInfo>();
    	apps = packageManager.getInstalledPackages(0);
    	for(int i = 0; i < apps.size(); i++)
    	{
    		String nameString = apps.get(i).packageName;
    		if(nameString.equals(packageName))
    		{
    			return true;
    		}
    	}
    	return false;
    }