--- title: Basic Queries slug: back4app/6RDt-_gOR0GPm6MoSHvhg description: In this guide, you'll learn how to perform basic data querying in Parse on a Android application image: https://www.back4app.com/images/logo-social.png createdAt: 2024-03-13T14:02:54.879Z --- # Basic Queries on Android ## Introduction In this guide, you will perform basic queries in `Parse` and implement an `Android` app using these queries. You will learn how to set up and query realistic data using `Back4App` and `Android`. This tutorial uses an app created in Android Studio 4.1.1 with `buildToolsVersion=30.0.2` , `Compile SDK Version = 30.0.2` and `targetSdkVersion=30` :::hint{type="success"} At any time, you can access the complete Android Project built with this tutorial at our Github repositories - [Kotlin Example Repository](https://github.com/templates-back4app/Android-Parse-Sdk-Kotlin) - [Java Example Repository](https://github.com/templates-back4app/Android-Parse-Sdk-Java) ::: ## Goal Our goal is query data stored on `Back4App` from an `Android` app. Here is a preview of what we are gonna achieve: ::Image[]{src="https://api.main.archbee.co/api/optimize/yD3zCY-NNBBIfd0uqcfR5/2P-b0YNHro11-ifKLt8YQ_image.png" size="50" width="346" height="750" position="center" showCaption="false"} ## Prerequisites :::hint{type="info"} **To complete this tutorial, we need:** - [Android Studio](https://developer.android.com/studio/index.html) - An app created on Back4App. - **Note: **Follow the [New Parse App tutorial](https://www.back4app.com/docs/get-started/new-parse-app) to learn how to create a Parse App on Back4App. - An android app connected to Back4App. - **Note: **Follow the [Install Parse SDK tutoria](https://www.back4app.com/docs/android/parse-android-sdk)l to create an Android Studio Project connected to Back4App. - A device (or[ virtual device](https://developer.android.com/studio/run/managing-avds.html)) running Android 4.1 (Jelly Bean) or newer. ::: ## Let’s get started! :::hint{type="info"} Before next steps, we need to connect `Back4App` to our application. You should save the `appId` and `clientKey` from the `Back4App` to `string.xml` file and then init `Parse` in our `App.java` or `App.kt` file. Follow the [New Parse App tutorial](https://www.back4app.com/docs/android/parse-android-sdk) if you don’t know how to init `Parse` to your app. Or you can download the projects we shared the github links above and edit only the `appId` and `clientKey` parts according to you. ::: ## 1 - Understanding the Parse.Query class Any Parse query operation uses the `ParseQuery` object type, which will help you retrieve specific data from your database throughout your app. It is crucial to know that a `ParseQuery` will only resolve after calling a retrieve method (like `query.findInBackground`), so a query can be set up and several modifiers can be chained before actually being called. To create a new `ParseQuery`, you need to pass as a parameter the desired ParseObject subclass, which is the one that will contain your query results. An example query can be seen below, in which a fictional Profile subclass is being queried. :::CodeblockTabs ```java 1 // This will create your query 2 ParseQuery query = new ParseQuery<>("Profile"); 3 // The query will resolve only after calling this method 4 query.findInBackground(); ``` ```kotlin 1 // This will create your query 2 val query = ParseQuery("Profile") 3 // The query will resolve only after calling this method 4 query.findInBackground() ``` ::: You can read more about the `Parse.Query` class [here at the official documentation](https://www.back4app.com/docs/javascript/parse-javascript-sdk). ## 2 - Save some data on Back4App :::hint{type="info"} In this step, we will create a Class with the JS Console and Javascript codes provided by `Parse` and we will create queries for this Class. ::: Let’s create a `Profile` class, which will be the target of our queries in this guide. On `Parse` Dashboard Javascript Console is possible to run JavaScript code directly, querying and updating your application database contents using the JS SDK commands. Run the code below from your JS Console and insert the data on Back4App. Here is how the JS Console looks like in your dashboard: ![](https://api.main.archbee.co/api/optimize/yD3zCY-NNBBIfd0uqcfR5/Wlu7TX7N6ZuOhocNdNmrc_image.png) Go ahead and create the user`Profile`class with the following example content: ```java 1 // Add Profile objects and create table 2 // Adam Sandler 3 let Profile = new Parse.Object('Profile'); 4 Profile.set('name', 'Adam Sandler'); 5 Profile.set('birthDay', new Date('09/09/1966')); 6 Profile.set('friendCount', 2); 7 Profile.set('favoriteFoods', ['Lobster', 'Bread']); 8 await Profile.save(); 9 10 // Adam Levine 11 Profile = new Parse.Object('Profile'); 12 Profile.set('name', 'Adam Levine'); 13 Profile.set('birthDay', new Date('03/18/1979')); 14 Profile.set('friendCount', 52); 15 Profile.set('favoriteFoods', ['Cake', 'Bread']); 16 await Profile.save(); 17 18 // Carson Kressley 19 Profile = new Parse.Object('Profile'); 20 Profile.set('name', 'Carson Kressley'); 21 Profile.set('birthDay', new Date('11/11/1969')); 22 Profile.set('friendCount', 12); 23 Profile.set('favoriteFoods', ['Fish', 'Cookies']); 24 await Profile.save(); 25 26 // Dan Aykroyd 27 Profile = new Parse.Object('Profile'); 28 Profile.set('name', 'Dan Aykroyd'); 29 Profile.set('birthDay', new Date('07/01/1952')); 30 Profile.set('friendCount', 66); 31 Profile.set('favoriteFoods', ['Jam', 'Peanut Butter']); 32 await Profile.save(); 33 34 // Eddie Murphy 35 Profile = new Parse.Object('Profile'); 36 Profile.set('name', 'Eddie Murphy'); 37 Profile.set('birthDay', new Date('04/03/1961')); 38 Profile.set('friendCount', 49); 39 Profile.set('favoriteFoods', ['Lettuce', 'Pepper']); 40 await Profile.save(); 41 42 // Fergie 43 Profile = new Parse.Object('Profile'); 44 Profile.set('name', 'Fergie'); 45 Profile.set('birthDay', new Date('03/27/1975')); 46 Profile.set('friendCount', 55); 47 Profile.set('favoriteFoods', ['Lobster', 'Shrimp']); 48 await Profile.save(); 49 50 console.log('Success!'); ``` ### 3 - Query the data Now that you have a populated class, we can now perform some basic queries in it. Let’s begin by filtering `Profile` results by name, which is a string type field, searching for values that contain the name `Adam` using the `Parse.Query.contains` method: ```java 1 // Create your query 2 let parseQuery = new Parse.Query('Profile'); 3 4 // `contains` is a basic query method that checks if string field 5 // contains a specific substring 6 parseQuery.contains('name', 'Adam'); 7 8 // The query will resolve only after calling this method, retrieving 9 // an array of `Parse.Objects` 10 let queryResults = await parseQuery.find(); 11 12 // Let's show the results 13 for (let result of queryResults) { 14 // You access `Parse.Objects` attributes by using `.get` 15 console.log(result.get('name')); 16 }; ``` Let’s now query by the number type field `friendCount` by using another common query method, `Parse.Query.greaterThan`. In this case, we want user `Profiles` in which the friend count is greater than 20. ```java 1 // Create your query 2 let parseQuery = new Parse.Query('Profile'); 3 4 // `greaterThan` is a basic query method that does what it 5 // says on the tin 6 parseQuery.greaterThan('friendCount', 20); 7 8 // The query will resolve only after calling this method, retrieving 9 // an array of `Parse.Objects` 10 let queryResults = await parseQuery.find(); 11 12 // Let's show the results 13 for (let result of queryResults) { 14 // You access `Parse.Objects` attributes by using `.get` 15 console.log(`name: ${result.get('name')}, friend count: ${result.get('friendCount')}`); 16 }; ``` Other recurring query methods are `Parse.Query.ascending` and `Parse.Query.descending`, responsible for ordering your queries. This ordering can be done in most data types, so let’s order a query by the date field `birthDay` by the youngest. ```java 1 // Create your query 2 let parseQuery = new Parse.Query('Profile'); 3 4 // `descending` and `ascending` can and should be chained 5 // with other query methods to improve your queries 6 parseQuery.descending('birthDay'); 7 8 // The query will resolve only after calling this method, retrieving 9 // an array of `Parse.Objects` 10 let queryResults = await parseQuery.find(); 11 12 // Let's show the results 13 for (let result of queryResults) { 14 // You access `Parse.Objects` attributes by using `.get` 15 console.log(`name: ${result.get('name')}, birthday: ${result.get('birthDay')}`); 16 }; ``` As stated here before, you can and should chain query methods to achieve more refined results. Let’s then combine the previous examples in a single query request: ```java 1 // Create your query 2 let parseQuery = new Parse.Query('Profile'); 3 4 parseQuery.contains('name', 'Adam'); 5 parseQuery.greaterThan('friendCount', 20); 6 parseQuery.descending('birthDay'); 7 8 // The query will resolve only after calling this method, retrieving 9 // an array of `Parse.Objects` 10 let queryResults = await parseQuery.find(); 11 12 // Let's show the results 13 for (let result of queryResults) { 14 // You access `Parse.Objects` attributes by using `.get` 15 console.log(`name: ${result.get('name')}, friend count: ${result.get('friendCount')}, birthday: ${result.get('birthDay')}`); 16 }; ``` ## 4 - Query from our Android App We will now do the operations we did above from the JS Console with Java and Kotlin in our Android application. We will list the profiles by making 4 different queries. :::CodeblockTabs ```java 1 private void doQueryByName() { 2 ParseQuery query = new ParseQuery<>("Profile"); 3 query.whereContains("name", "Adam"); 4 progressDialog.show(); 5 query.findInBackground((objects, e) -> { 6 progressDialog.hide(); 7 if (e == null) { 8 adapter = new ResultAdapter(this, objects); 9 resultList.setLayoutManager(new LinearLayoutManager(this)); 10 resultList.setAdapter(adapter); 11 } else { 12 Toast.makeText(this, e.getLocalizedMessage(), Toast.LENGTH_SHORT).show(); 13 } 14 }); 15 } 16 17 private void doQueryByFriendCount() { 18 ParseQuery query = new ParseQuery<>("Profile"); 19 query.whereGreaterThan("friendCount", 20); 20 progressDialog.show(); 21 query.findInBackground((objects, e) -> { 22 progressDialog.hide(); 23 if (e == null) { 24 adapter = new ResultAdapter(this, objects); 25 resultList.setLayoutManager(new LinearLayoutManager(this)); 26 resultList.setAdapter(adapter); 27 } else { 28 Toast.makeText(this, e.getLocalizedMessage(), Toast.LENGTH_SHORT).show(); 29 } 30 }); 31 } 32 33 private void doQueryByOrdering() { 34 ParseQuery query = new ParseQuery<>("Profile"); 35 query.orderByDescending("birthDay"); 36 progressDialog.show(); 37 query.findInBackground((objects, e) -> { 38 progressDialog.hide(); 39 if (e == null) { 40 adapter = new ResultAdapter(this, objects); 41 resultList.setLayoutManager(new LinearLayoutManager(this)); 42 resultList.setAdapter(adapter); 43 } else { 44 Toast.makeText(this, e.getLocalizedMessage(), Toast.LENGTH_SHORT).show(); 45 } 46 }); 47 } 48 49 private void doQueryByAll() { 50 ParseQuery query = new ParseQuery<>("Profile"); 51 query.whereContains("name", "Adam"); 52 query.whereGreaterThan("friendCount", 20); 53 query.orderByDescending("birthDay"); 54 progressDialog.show(); 55 56 query.findInBackground((objects, e) -> { 57 progressDialog.hide(); 58 59 if (e == null) { 60 adapter = new ResultAdapter(this, objects); 61 resultList.setLayoutManager(new LinearLayoutManager(this)); 62 resultList.setAdapter(adapter); 63 resultList.setNestedScrollingEnabled(false); 64 } else { 65 Toast.makeText(this, e.getLocalizedMessage(), Toast.LENGTH_SHORT).show(); 66 } 67 }); 68 } ``` ```kotlin 1 private fun doQueryByName() { 2 val query = ParseQuery("Profile") 3 query.whereContains("name", "Adam") 4 progressDialog!!.show() 5 query.findInBackground { objects: List?, e: ParseException? -> 6 progressDialog!!.hide() 7 if (e == null) { 8 adapter = ResultAdapter(this, objects) 9 resultList!!.layoutManager = LinearLayoutManager(this) 10 resultList!!.adapter = adapter 11 } else { 12 Toast.makeText(this, e.localizedMessage, Toast.LENGTH_SHORT).show() 13 } 14 } 15 } 16 17 private fun doQueryByFriendCount() { 18 val query = ParseQuery("Profile") 19 query.whereGreaterThan("friendCount", 20) 20 progressDialog!!.show() 21 query.findInBackground { objects: List?, e: ParseException? -> 22 progressDialog!!.hide() 23 if (e == null) { 24 adapter = ResultAdapter(this, objects) 25 resultList!!.layoutManager = LinearLayoutManager(this) 26 resultList!!.adapter = adapter 27 } else { 28 Toast.makeText(this, e.localizedMessage, Toast.LENGTH_SHORT).show() 29 } 30 } 31 } 32 33 private fun doQueryByOrdering() { 34 val query = ParseQuery("Profile") 35 query.orderByDescending("birthDay") 36 progressDialog!!.show() 37 query.findInBackground { objects: List?, e: ParseException? -> 38 progressDialog!!.hide() 39 if (e == null) { 40 adapter = ResultAdapter(this, objects) 41 resultList!!.layoutManager = LinearLayoutManager(this) 42 resultList!!.adapter = adapter 43 } else { 44 Toast.makeText(this, e.localizedMessage, Toast.LENGTH_SHORT).show() 45 } 46 } 47 } 48 49 private fun doQueryByAll() { 50 val query = ParseQuery("Profile") 51 query.whereContains("name", "Adam") 52 query.whereGreaterThan("friendCount", 20) 53 query.orderByDescending("birthDay") 54 progressDialog!!.show() 55 query.findInBackground { objects: List?, e: ParseException? -> 56 progressDialog!!.hide() 57 if (e == null) { 58 adapter = ResultAdapter(this, objects) 59 resultList!!.layoutManager = LinearLayoutManager(this) 60 resultList!!.adapter = adapter 61 resultList!!.isNestedScrollingEnabled = false 62 } else { 63 Toast.makeText(this, e.localizedMessage, Toast.LENGTH_SHORT).show() 64 } 65 } 66 } ``` ::: ## It’s done! At the end of this guide, you learned how basic data queries work on Parse and how to perform them on Back4App from an Android App.