Developer android freelancer仕事

絞り込む

私の最近の検索
次の条件で絞り込む:
予算
to
to
to
種類
スキル
言語
    ジョブステータス
    2,000 developer android freelancer 仕事が見つかりました。次の価格: USD

    I'm in urgent need of an Android developer to help me implement an Free trial subscription model for my app. Key Requirements: Looking for experienced Android developer to fix the issue with Free trial subscriptions implementation. We have published and app that has free trial. All the free trials are getting to "Payment pending " state. We want developer to understand the issue and fix Please check the app here before you bid and discuss Ideal Candidate: - Proven experience working with Android subscriptions. - Familiarity with in-app purchases and subscription models. - Able to work under tight deadlines. - Experience in implementing exclusive content and ad-free experiences for subscribers is a plus.

    $108 (Avg Bid)
    $108 平均入札額
    9 入札

    I am in need of an expert Flutter UI developer to craft a straightforward and intuitive interface for a Laundry Service application on iOS and Android. Your work will involve developing an easy-to-navigate UI which is already designed on figma, that encapsulates simplicity and enhances user productivity. – Required Skills and Experience: • Proven experience in developing UIs in Flutter. • Strong knowledge of iOS and Android development. • Solid understanding of intuitive and simplistic interface design. • Prior experience in the productivity app category beneficial but not mandatory. To submit an informed bid, please provide a brief of your Flutter UI development process and any relevant work in the productivity application sector.

    $167 (Avg Bid)
    $167 平均入札額
    31 入札

    More details: Is this project for business or personal use? For starting a new enterprise What information should successful freelancers include in their application? Detailed project proposals How soon do you need your project completed? ASAP

    $12 / hr (Avg Bid)
    $12 / hr 平均入札額
    30 入札

    I am in need of a proficient web developer to assist me with a project. The exact nature of the site is undecided, but your background in several types of website development will serve you well. Here's what I'm looking for: - Versatility: Since I haven't settled on a specific type of website yet, your flexibility and adaptability in website creation is beneficial. - Solid experience in website development: Having a rich portfolio will be an advantage. - No strict deadlines: There is no time limit for project completion. That said, an efficient, self-directed approach to work is appreciated. Join me in this steady, long-term collaboration. Looking forward to your pitches.

    $114 (Avg Bid)
    $114 平均入札額
    34 入札

    I want to write an application like a motivation letter to show my interest in a job advert I applied for. these headings will be. 1. Who I am 2. My linkedin profile 3. My expertise in mobile app 4. Why I want to be a part of your compay 5. Why I want this position ? 6. Why You should hire me.

    $18 (Avg Bid)
    $18 平均入札額
    7 入札

    ...capable hand to create an AI tool for an Android game that's similar to Subway Surfers. This tool should be built to perform at an intermediate level, hence, it shouldn't struggle with achieving basic tasks but doesn't have to excel at the hardest ones. The ideal freelancer for this job should have experience a deep understanding of artificial intelligence. Key Requirements: - AI Character Movement: The tool must automate the character's movements throughout the game. - Collecting Power-Ups: The AI tool should be clever enough to identify and collect power-ups. - Dodging Obstacles: It is essential that the tool ensures the character constantly avoids obstacles to prolong gameplay. Please note, it's crucial that the tool works seamlessly on ...

    $89 (Avg Bid)
    $89 平均入札額
    3 入札

    We need a new PHP microservice, which will serve as a stateless proxy to communicate with payment gateway. This microservice should expose endpoints to create new payment, check its status, etc. This microservice will only proxy the request, there is no need for a database or a queue. Currently we have a web, Android and iOS applications, which will all communicate with this new microservice in order to provide "pay" functionality for the users. Payment gateway to be used: Global Payments Payment methods we need to support: redirect to payment gateway, Apple pay, Google pay, pay later Technical specification with all of the requirements can be found in attachment.

    $575 (Avg Bid)
    $575 平均入札額
    71 入札

    I'm in need of a skilled app developer to create a cross-platform (iOS and Android) application. The main function of the app will be to provide prayer times. Key Requirements: - App should display accurate and timely prayer times. - The app should support both preset location-specific prayer times and allow users to adjust for their specific location. Ideal Skills and Experience: - Proficiency in cross-platform app development (iOS and Android). - Experience working on applications with a strong focus on accurate data and real-time updates. - Familiarity with geolocation and time zone conversion is highly desirable. - Knowledge of UI/UX best practices to ensure a user-friendly experience.

    $403 (Avg Bid)
    $403 平均入札額
    21 入札

    As an innovative thinker, I require a proficient app developer to create a basic application for both iPhone and Android. The fundamental purpose of this app is to establish a seamless connection with a Bluetooth source (specifically, an esp32 sending sensor and pin status data) and store the received data in a local CSV file on the phone. Key Feature Requirements: - The app should function smoothly on both Android and iPhone platforms. (priority is android for now) - Ability to connect over Bluetooth with an esp32 wroom module. The Bluetooth protocol may be either BLE or classic, as I am not entirely certain which one this module uses. - Once connected, the app should be capable of receiving sensor and pin status data. - The app should store this received da...

    $25 - $314
    特集 緊急 シール
    $25 - $314
    26 入札

    I'm looking for an experienced Odoo Developer who can help me integrate multiple functionalities into my system, including Sales and CRM, Inventory Management, and Accounting and Finance. Key Responsibilities: - Implement Sales and CRM module: This will include managing leads, opportunities, and customer follow-up. - Inventory Management: This entails overseeing product movements, order fulfillment, and stock valuations. - Accounting and Finance: Handling invoicing, budget management, and financial analysis will form a crucial part of your duties. Moreover, I require these systems to be seamlessly integrated with my existing Email marketing tool and Customer support platform. Experience and Skills required: - Proven Odoo development experience. This should be demonstrate...

    $742 (Avg Bid)
    $742 平均入札額
    15 入札

    I am seeking an experienced Android developer who can help build a real-time request tracking system. The goal is to provide users with accurate, up-to-date location details. Key Features: - Real-time tracking - Location history - Push notifications These are the core elements I am looking for. I am particularly in need of someone who has a firm grasp of Java and Kotlin, as these are the primary technologies I prefer for this project. Please, in your application, provide your past experiences, particularly those relevant to these needs. Detailed project proposals are also welcome. Skills and Experience: - Proven experience as an Android developer - Proficiency in Java and Kotlin - Experience in real-time location tracking systems will be a plus I look for...

    $77 (Avg Bid)
    $77 平均入札額
    8 入札

    Urgente presupuesto 60 dólares realizado estos cambios o mejoras o corregir errores Todos los requisitos de una App o Uso de una API. o Hacer un gráfico. o Modo día/noche. o Seguridad mediante Shared Preferences. o Validación de formularios. o Búsqueda de datos mediante filtros. o Evitar datos duplicados. o Uso de semáforos. o Uso de notificaciones.  Crear un chat (público y privado) para los usuarios de la aplicación.

    $6 / hr (Avg Bid)
    $6 / hr 平均入札額
    9 入札

    We are a newly established IT consulting company based in the UAE, specializing in consulting, software development, and IT services. We are seeking a skilled and experienced freelancer who can assist us in generating leads and driving sales for our business. Responsibilities: Conduct market research to identify potential clients and industries that could benefit from our services. Develop and implement effective lead generation strategies tailored to our target market. Utilize various channels such as social media, email marketing, cold calling, and networking to reach potential clients. Qualify leads and nurture them through the sales funnel, from initial contact to closing deals. Collaborate with our team to develop compelling sales pitches and presentations. Track and analyze ...

    $1032 (Avg Bid)
    $1032 平均入札額
    25 入札

    I'm in the process of developing a new app that primarily focuses on reminding users for prayer times. It will also collect Quran citations, remembrance...reminding users for prayer times. It will also collect Quran citations, remembrances, and showcase the Qibla. The app is aimed at engaging anyone interested in improving their Islamic rituals and prayers regardless of their familiarity with the Quran or Islamic teachings. Here's what I'm looking for in a successful freelancer: a * Knowledge and respect for Islamic culture * Creative thinker with prior experience in app naming * Understanding of app platform constraints (iOS and Android) Ultimately, I need a captivating, easily searchable, and culturally appropriate name that represents the app's purpo...

    $29 (Avg Bid)
    $29 平均入札額
    11 入札

    I am seeking a Python developer with expertise in image processing and Pytorch to assist with AI image processing in Python code. Key Requirements: - Skilled in Python programming - Proficient in Pytorch - Experience with image processing using AI - Ability to work with and integrate AI image processing code The task involves handling image processing tasks using AI, most likely image classification, object detection and segmentation. The outcome of the task is to have a functioning AI image processing code. Please get in touch if you have the necessary expertise.

    $252 (Avg Bid)
    $252 平均入札額
    49 入札

    I'm seeking a skilled developer to support in building a comprehensive fitness app that will include workout tracking capabilities and detailed data analytics. Key Features: - **Workout Tracking**: The app should be able to track key metrics such as duration, distance, calories burned, and effort/strain during workouts. - **Data Analytics & Comparison**: This is a crucial component of the app. It should allow users to: - Compare their current workout with previous ones. - Compare their workout with other users. - Track their progress over time. The ideal candidate should have experience in developing fitness applications, strong backend development skills, and the ability to create native IOS and Android applications. A good understanding of data analytics an...

    $39668 (Avg Bid)
    $39668 平均入札額
    120 入札

    I'm in urgent need of an experienced Java developer for a single day job to enhance a couple of capabilities in a data management feature within an existing API. Responsibilities include: - Diagnosing the current API functionality - Refactoring a portion of the code - Developing and testing enhancements to increase its capabilities Skills and experience needed: - Proven experience as a full stack Java developer - Pattern recognition and problem-solving skills in Java/APIs - Adept at data management within APIs - Strong communication to provide updates on your progress The aim is not to only get the task completed but to improve performance and efficiency in the long run.

    $6 / hr (Avg Bid)
    $6 / hr 平均入札額
    17 入札

    I am in search of a talented developer, well-versed in YoKart platform. I am primarily focusing on building an effective e-commerce platform. I do expect these from you: - extensive experience in YoKart, especially in setting up e-commerce. - Develop a product catalog, shopping cart, and ensure payment gateway integration. In your application, I would like to know more about your experience with YoKart. Bid with confidence if you have the necessary skills. It would be great if the candidate was an was an ex-employee of Fatbit.

    $8 / hr (Avg Bid)
    $8 / hr 平均入札額
    11 入札

    I'm in need of a talented mobile app developer who can create an extensive lottery results application for both Android and Apple devices. The app must provide detailed real-time results for Powerball, Mega Millions, and Euro Millions. Key Features: - Shows real-time updates for winning numbers, jackpot amounts and prize breakdowns. - Displays latest lotto results and jackpots. - Allows users to scan their tickets and manually enter their numbers. - Provides statistics by number for users to track their chances. - Multilingual support to cater to a global audience. - Includes of an ad-supported version with a Pro upgrade option offering an ad-free experience and additional features. - Account membership and ability to save up to 50 lines of previous results. I also pr...

    $799 (Avg Bid)
    $799 平均入札額
    79 入札

    I have a script written in : - **Frontend**: , TypeScript, TailwindCSS - **Backend**: TRPC, PrismaORM, Postgresql, NextAuth - **AI**: OpenAI's DALL-E2 - **Storage**: Amazon S3 - **Payment**: Stripe I want somebody to : Change Gmail to Email / Password authendication Change AmazonS3 to local files hosting Change stripe to add 3 more pages at the bottom : Terms of Service , Refund Policy , Privacy Policy and setup it on a cpanel hosting or in a vps for me.

    $245 (Avg Bid)
    $245 平均入札額
    69 入札

    I'm looking for an expert in the HR module of ERPNext to enhance our current system. Our main focus is to optimize the HR functionalities. We require an experienced professional who can tailor the ERPNext's HR module to include: - An employee self-service portal - Recruitment and onboarding support - Performance management system - Asset management The successful candidate should be adept at customizing these modules to blend seamlessly with our current workflow. Please note, the scale of the project, in terms of the number of employees and assets, will be communicated upon further discussions.

    $7 / hr (Avg Bid)
    $7 / hr 平均入札額
    53 入札

    I am in need of a talented, individual developer based in Indore who is proficient with both Joomla and Magento platforms to build and develop my website. In particular, the website needs to have: - E-commerce functionality: enabling purchase of goods and services online. - Responsive design: optimized for viewing on a variety of devices and window or screen sizes. - Customizable templates: flexible design elements to accommodate changing needs and preferences. Ideal candidates should have significant experience in using Joomla and Magento, and provide examples of past projects demonstrating these skills. Detailed project proposals are also highly welcomed.

    $8 / hr (Avg Bid)
    $8 / hr 平均入札額
    12 入札

    We're currently looking for a proficient Shopify Developer to handle a App integration and Payment Gateway setup. Our primary goal for the Shopify store, while not yet specified, could be any or all of the following - increase online sales, build brand awareness, improve customer experience. As such, we're looking for a reliable and experienced candidate who can provide dynamic solutions for a variety of possible objectives. We appreciate your interest and look forward to viewing your applications!

    $122 (Avg Bid)
    $122 平均入札額
    50 入札

    I need an innovative Android app developer who will create an app to extract interaction chains from another app. This is for research purposes. The main focus is to analyze the types of interactions within the targeted app. Specifically, the app should record detailed chains of user interaction. Ideal skills for this job would include extensive experience in Android app development, a deep understanding of data extraction methods, as well as a good grasp of user behavior analysis. In addition to these skills, experience in data driven research would be highly advantageous. Your role will not be limited to just creating an app, but to bring a research tool to life. This project is more than creating an app; it's an exploration into understanding users better.

    $307 (Avg Bid)
    $307 平均入札額
    41 入札

    I'm in search of a professional freelancer who can assist me with my project. The primary goal of this project is to generate leads for my business. The ideal freelancer will have: - Proven experience with generating leads - A vast and varied portfolio of past projects - Strong communication skills When applying, please ensure to include your past work. I'll be searching for a freelancer who can not only meet but exceed my expectations.

    $249 (Avg Bid)
    $249 平均入札額
    15 入札

    I'm seeking a Laravel developer to assist with updating the content of my website. The tasks involved is attached in the file . Thanks in advance for your bids. Looking forward to working with you.

    $59 (Avg Bid)
    $59 平均入札額
    52 入札

    ...Unity 3D developer with experience in creating card games, specifically within the battle card game genre. Key Requirements: - Develop a battle card game within Unity 3D from the ground up - Implement game mechanics that are typical of this genre - Create an engaging user interface and experience - Opportunity for further collaboration on game expansions and updates Ideal Skills: - Proven experience in developing card games, especially battle card games, in Unity 3D - Strong understanding of Unity 3D's capabilities and limitations - Ability to create polished, visually appealing game designs - Experience with multiplayer functionality is a plus This project requires someone who has a passion for card games and a good eye for engaging gameplay. It's important that the...

    $1678 (Avg Bid)
    $1678 平均入札額
    50 入札

    I urgently need a skilled CS-Cart developer to implement certain product management features on my website. This primarily includes: home products about category Although I did not specify needs concerning product categorization, stock management etc., knowledge of them would be a definite advantage. Experience in building similar features on CS-Cart platforms is a must. I'm looking to get the project done ASAP. If you have the expertise and can deliver quickly, I want to hear from you.

    $105 (Avg Bid)
    $105 平均入札額
    24 入札

    I'm looking for a qualified Wix Developer to build a clean and minimalistic static informative website. This website will serve as a reliable platform for customers to conveniently access information about our company and its services. It should comprise of the following pages: Home, About Us, Services, FAQ, and Contact Us. The final result should be user-friendly and aesthetically pleasing to maintain the site's simplicity that aligns with our brand. Proficiency in Wix website design and a keen eye for minimalistic yet attractive design layouts are crucial for this project.

    $52 (Avg Bid)
    $52 平均入札額
    18 入札

    I'm in search of a Senior Full Stack developer, passionate about their craft, to join our ranks. Your wealth of knowledge and experience will be the key to our growth and the solution to surpassing our current limitations. Key Skills: - Proficiency in JavaScript, C#, React, Vue, and .NET Core - Familiarity with Visual Studio - Experience in MySQL database management Nice to have ● Familiarity with DevOps and CI/CD pipeline. ● Familiarity with containerization tools like Docker and Kubernetes. ● Frontend development experience working with React.js. What you have ● 8+ years of experience as a full stack engineer on a team using standard best practices. ● 5+ years of experience as a Full-stack engineer with .NET, ASP.Net Core, Azure, Angular, and React.js. ● Proficiency in a s...

    $20 / hr (Avg Bid)
    $20 / hr 平均入札額
    157 入札

    I am looking for someone to make a game with me

    $5 / hr (Avg Bid)
    $5 / hr 平均入札額
    35 入札

    I am in need of a skilled .NET developer who can help me with my web development project. The focus is on web development using ASP.NET MVC. Key Requirements: - ASP.NET MVC Experience: You must have a strong background in ASP.NET MVC. This is the technology stack we are using for this project. - 3rd Party Integration: The project requires seamless integration with financial management applications. Therefore, experience in integrating third-party services in a web environment will be crucial. Please note that while experience in Blazor or ASP.NET Web Forms is appreciated, it is not essential for this specific project. Your role as the developer will be to assist in building the application, ensuring the highest quality code, and making sure the application is fully inte...

    $5 / hr (Avg Bid)
    $5 / hr 平均入札額
    42 入札

    I'm in need of an expert to help me set up an Android application that can stream live audio broadcasts. This will be done using the gstreamer library, specifically focusing on AAC audio format. Key Responsibilities: - Develop an Android application that can handle live audio streaming. - Integrate gstreamer library to facilitate AAC audio streaming. - Ensure the application is capable of high-quality audio output. Ideal Skills and Experience: - Strong background in Android app development. - Proficiency in working with gstreamer library for audio streaming. - Prior experience with live audio broadcasting applications. - Understanding of AAC audio format and its implementation in Android.

    $598 (Avg Bid)
    $598 平均入札額
    61 入札

    I'm currently looking for a skilled WordPress developer to help me with my website. 1. Color options needs to be hidden for now from product archive page. Not in single product view page. 2. Need a second Product name when after clicking add to card. for example: product name (Mens T-shirt - Blue) it should display (Mens T-shirt) When the buyer clicks add to cart. 3. Need to add filer on Product Archive page Feel free to include any additional information about your experience, tools, or methods you use that you feel would be relevant to this project. Looking forward to working with you.

    $114 (Avg Bid)
    $114 平均入札額
    84 入札

    I'm looking for an experienced backend developer to handle database management and API integration for my project. Key Responsibilities: - Implement and manage a MySQL database efficiently. - Develop and integrate APIs to ensure seamless communication between front-end and database. Ideal Skills: - Proficiency in MySQL is a must. - Strong experience in API integration. Experience with other databases and backend technologies like Python, Java, and Node.js would be a plus. The chosen freelancer will need to understand the project's requirements thoroughly and communicate effectively with the front-end team to ensure a well-functioning, reliable backend system.

    $307 (Avg Bid)
    $307 平均入札額
    52 入札

    1. Design and develop Google toolkits by ourselves 2. Subject matter is not limited 3. The total number of pages is not more than 10, the size is not more than 18M 4. Programming language is not limited, kotlin is the best 5. Also Acquisition of Google Developer Account and Google Toolkit

    $563 (Avg Bid)
    $563 平均入札額
    14 入札

    1. Record call 2 side 2. Work in android 13, 14 3. Get histroy call and contacts 4. Save calls and send to sftp or ssl or .... 5. Clear record calls auto after send 6. Hide in menu

    $1179 (Avg Bid)
    $1179 平均入札額
    74 入札

    I'm looking for a skilled game developer to create an aviator game for Windows, Mac, and Mobile (iOS/Android). The game genre should be centered around a flight simulator, with a focus on realism and user engagement. Key Features: - Realistic Weather Conditions: The game should incorporate real-time weather conditions that affect flight performance, adding an extra layer of challenge and authenticity. - Multiple Aircraft Types: To cater to a broad audience, the game should offer a diverse range of aircraft for players to choose from. Each aircraft should have unique characteristics and handling. - Global Airports: The game should feature a variety of airports from around the world, each with its own layout, challenges, and atmosphere. Ideal Skills and Experience: - Ex...

    $1297 (Avg Bid)
    $1297 平均入札額
    9 入札

    I am on the lookout for an experienced Java developer to work on small web development projects related to my business. Your tasks will primarily revolve around: Working knowledge of JSF/Primefaces and JPA. Experience with HTML/CSS.

    $5 / hr (Avg Bid)
    $5 / hr 平均入札額
    29 入札

    Looking for a react developer to fix the issue in my website. it is a informative website

    $11 / hr (Avg Bid)
    $11 / hr 平均入札額
    113 入札

    Looking for a developer who has experience in the below tech skill-set Frontend Angular Typescript Backend PostgreSQL Third-party integration Stripe OpenAI Cloud AWS

    $200 (Avg Bid)
    $200 平均入札額
    1 入札

    In need of an experienced inDesign freelancer to assist with a paperback format of a book. I have a simple docx file approx 200 Pages. Need this within 24 hours. Please don't bid if you are not agree with this requirement.

    $12 (Avg Bid)
    $12 平均入札額
    9 入札

    I'm looking for a seasoned developer to transfer my current Xamarin-based application to Flutter for both Android and iOS. Key Features: - The migrated application must preserve the existing functionality. This includes user authentication, data synchronization, and push notifications. Platform Compatibility: - The finished product must be compatible with the latest versions of Android and iOS (Android 10 and iOS 14 specifically). Design Assistance: - While I do possess several ideas for the new UI/UX, professional guidance is needed. An eye for modern, user-friendly design and experience in UI/UX would be advantageous. Ideal candidates would have proven expertise in both Xamarin and Flutter and a keen understanding of Android and iOS...

    $2331 (Avg Bid)
    $2331 平均入札額
    142 入札

    Requirements will be provided -Setup backend database in snowflake -Develop functional UI -Develop Admin UI -Develop Vendor UI Assist in game launch, testing and revising in feedback

    $21 / hr (Avg Bid)
    $21 / hr 平均入札額
    84 入札

    I'm seeking a professional mobile app developer to create an app that will serve as a productivity tool. Please provide: - Examples of your past work - Relevant experience - Detailed project proposals The app should be developed for both Android and iOS platforms. Skills and experience required: - Extensive experience in mobile app development - Strong understanding of usability and user experience - Proficiency in developing for both Android and iOS - Excellent communication skills.

    $19576 (Avg Bid)
    $19576 平均入札額
    43 入札

    I'm looking for an experienced mobile app developer who can create a versatile app for both iOS and Android. The primary function of this app is to help users manage their account balance. This will involve allowing users to view their current balance, deposit and withdraw funds, and receive real-time notifications about their account activity. Ideal skills: - Proficient in creating apps for both iOS and Android - Experience with account management and notification systems - Ability to design and develop user-friendly interfaces I'm open to suggestions on how to best implement these features and ensure a smooth user experience. Please provide examples of similar projects you have worked on in the past. Here some informations about the project: I need ...

    $415 (Avg Bid)
    $415 平均入札額
    84 入札

    In this project, I'm in search of a skilled and experienced React Native developer who can do bug fixing in my already developed Android application. Moreover, the developer needs to embed an OTP-based login system for the app. Specifically: - The developer should be proficient in React Native, Android development, and fixing bugs. - Knowledge of implementing OTP-based login functionality is also needed. - Past experience in resolving application bugs and enhancing functionalities is highly preferred for successful completion of these tasks. The main aim of this project is to resolve the existing bugs making the app more efficient and user-friendly.

    $103 (Avg Bid)
    $103 平均入札額
    22 入札

    Need a Android app developer to work on a simple e-commerce app similar to bewakoof app Pages are home, categories, products list, product details, cart, checkout, login, razorpay payment gateway

    $176 (Avg Bid)
    $176 平均入札額
    42 入札

    I need a MEAN stack developer who has very good knowledge in node.js and angular . My project is at ending stage . I need developer to fix issues and help in process to make application live . It will be a long term project if developer proves to be worthy . My application has following webstack - Node.js -Express -MongoDB -Angular It would be nice , Person has a good working experince in WEBRTC , chrome extension , powershell The project is time-sensitive and will require a dedicated developer to assist in expediting the process of completion. Ideal Skills: - Strong experience in full-stack development with the MEAN stack - Ability to prioritize tasks and deliver results under tight deadlines - Excellent communication skills for collaboration and u...

    $5 / hr (Avg Bid)
    $5 / hr 平均入札額
    46 入札

    I'm looking for an experienced Python developer to help with an image processing and machine learning project. - The primary goal of the project is object detection. - Specifically, I need to detect mouths in images. - The developer will need to use machine learning techniques to train a model to detect this specific object, and then implement it for processing images. - The ideal candidate should have experience with image processing, machine learning, and Python programming.

    $217 (Avg Bid)
    $217 平均入札額
    15 入札