Finish all intents android

Некоторые возможности использования Intent’ов

Введение

Объекты типа Intent могут быть использованы для общения между отдельными частями Android приложения, либо между различными приложениями системы. Мощь механизма интентов заключается в том, что с его помощью можно обращаться к любому установленному в системе приложению. Это позволяет повторно использовать некоторые компоненты и значительно сократить время на разработку.

В этой статье я покажу некоторые возможности использования класса Intent для обращения к системным приложениям.

Итак, что можно сделать с помощью Intenta:

1. Позвонить

Необходимо также добавить разрешение совершать звонки:

Либо разрешение для экстренных вызовов:

Звонки можно также совершать, указав интенту первый параметр как ACTION_DIAL. При этом будет открываться телефонная книга с указанным номером, но сам звонок автоматически совершаться не будет. Этому параметру не нужны разрешения в манифесте.

2. Отправить смс

Т.к. этот код не отправляет смс напрямую, а запускает стандартное активити для отправки смс, то никаких разрешений указывать не нужно.

3. Получить контакт из телефонной книги

Этот код откроет стандартное приложение контактов. Метод startActivityForResult позволяет получить uri выбранного контакт из параметра Intent data переопределенного метода onActivityResult.

Приведенный выше код показывает в приложении контактов сразу все контакты пользователя, включая почтовые. Если необходимо выбрать только контакт из телефонной книги, можно воспользоваться следующим кодом:

Для чтения списка контактов необходимо также добавить в манифест разрешение:

4. Открыть ссылку в браузере

Данный код откроет переданную в параметре ссылку в одном из установленных браузеров. При этом пользователь сможет сам выбрать браузер для просмотра. Eсли ссылка ведет на YouTube, то можно сразу открыть видео стандартным YouTube приложением.
С помощью этого интента можно также открыть стандартный клиент Android Market с ссылкой на какое-либо приложение. Для этого необходимо в параметр uri передать ссылку вида market://search?q=search query, где search query необходимо заменить соответствующим поисковым запросом.
Разрешения на интернет указывать не нужно, т.к. сеть используется не напрямую, а через приложение браузер.

5. Расшарить контент/написать письмо

Интенту можно задать тему и текст контента, который необходимо разшарить. Метод Intent.createChooser() создает диалог выбора соответствующего приложения.
Если необходимо разшарить медиа контент (изображение/видео), то нужно указать соответствующий тип контента в методе setType, например mailIntent.setType(«image/png»);, а также добавить сам контент в extra интента:

С помощью этого интента можно также отправить электронную почту по конкретному адресу:

6. Открыть карту по определенным координатам либо запросу

Uri при этом можно модифицировать, указывая другие параметры:

• geo:latitude,longitude
• geo:latitude,longitude?z=zoom Параметр z — уровень зума при отображении карты (от 0 до 23)
• geo:0,0?q=my+street+address
• geo:0,0?q=business+near+city

7. Сделать снимок с камеры

Этот код запускает стандартное приложение камеры. Полученное с камеры изображение можно обработать в методе onActivityResult:

Изображение, полученное с камеры при этом можно сохранить в конкретной директории, добавив параметр в интент:

Для использования этого интента не нужно разрешения android.permission.CAMERA, т.к. камера используется не напрямую, а всего лишь вызывается встроенное приложение камеры. Однако рекомендуется добавить в AndroidManifest следующую строку:

Таким образом, люди с девайсами без встроенной камеры (судя по всему, такое тоже бывает) не будут видеть ваше приложение на маркете.

8. Позвонить какому-либо контакту через Skype

Для совершения звонка через скайп интенту необходимо указать конкретное имя активити и пакета, к которым он будет обращаться. Это немного усложняет код, т.к. в двух разных версиях скайпа имена пакетов отличаются. Необходимо выполнять проверку того, какая версия скайп клиента установлена в системе, и установлена ли она вообще. Для проверки можно использовать следующий метод:

Этот метод проверяет в системе наличие приложения, способного ответить на конкретный интент. С использованием этого метода код звонка через скайп будет выглядеть следующим образом:

Более простым методом проверки наличия приложения в системе является перехват ActivityNotFoundException, которое будет вылетать в методе startActivity. Однако это позволит всего лишь среагировать на проблему, но не предотвратить ее. Например, используя вышеприведенный метод isIntentAvailable можно вовремя сделать соответствующий контрол неактивным, либо перенаправить пользователя на Android Market для установки соответствующего приложения.

9. Использовать Speech to Text для распознавания голоса

Этот код запускает приложение распознавания речи. Если произнести что-либо, система обработает голос и вернет результат в метод onActivityResult:

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Closing All Activities and Launching Any Specific Activity

Often times, most apps have an option where all the activities of the current app are closed and any new specific activity is launched. For example, on logging out of the application, all the activities are closed and login activity is started to allow user to make any new session.

This can be done using few lines code with power of intents like this:

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7 years experience. 💻 Creator of various Open Source libraries on Android . 📝 Author of two technical books and 100+ articles on Android. 🎤 A passionate Public Speaker giving talks all over the world.

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Android Intents — Tutorial

Using Intents in Android. This tutorials describes the usage of intents to communicate between Android components.

1. Starting other Android components via intents

1.1. What are intents?

Android application components can connect to other Android applications. This connection is based on a task description represented by an Intent object.

Intents are asynchronous messages which allow application components to request functionality from other Android components. Intents allow you to interact with components from the same applications as well as with components contributed by other applications. For example, an activity can start an external activity for taking a picture.

Intents are objects of the android.content.Intent type. Your code can send them to the Android system defining the components you are targeting. For example, via the startActivity() method you can define that the intent should be used to start an activity.

An intent can contain data via a Bundle . This data can be used by the receiving component.

In Android the reuse of other application components is a concept known as task. An application can access other Android components to achieve a task. For example, from a component of your application you can trigger another component in the Android system, which manages photos, even if this component is not part of your application. In this component you select a photo and return to your application to use the selected photo.

Such a flow of events is depicted in the following graphic.

1.2. Starting activities or services

To start an activity, use the method startActivity(intent) . This method is defined on the Context object which Activity extends.

The following code demonstrates how you can start another activity via an intent.

Activities which are started by other Android activities are called sub-activities. This wording makes it easier to describe which activity is meant.

To start a services via intents, use the startService(Intent) method call.

1.3. Sending out explicit or implicit intents

Android supports explicit and implicit intents. An application can define the target component directly in the intent (explicit intent) or ask the Android system to evaluate registered components based on the intent data(implicit intents).

Explicit intents explicitly define the component which should be called by the Android system, by using the Java class as identifier. Explicit intents are typically used within an application as the classes in an application are controlled by the application developer. The following shows how to create an explicit intent and send it to the Android system to start an activity.

Implicit intents specify the action which should be performed and optionally data which provides content for the action. If an implicit intent is sent to the Android system, it searches for all components which are registered for the specific action and the fitting data type. If only one component is found, Android starts this component directly. If several components are identified by the Android system, the user will get a selection dialog and can decide which component should be used for the intent.

For example, the following tells the Android system to view a webpage. All installed web browsers should be registered to the corresponding intent data via an intent filter.

1.4. Determine valid intent receivers

Sometimes you want to determine if a component has registered for an intent. For example, you want to check if a certain intent receiver is available and in case a component is available, you enable a functionality in your application.

This check can be done via the PackageManager class.

The following example code checks if a component has registered for a certain intent. Construct your intent as you are desired to trigger it and pass it to the following method.

Based on the result you can adjust your application. For example, you could disable or hide certain menu items.

1.5. Intents as event triggers

Intents can be used to send broadcast messages into the Android system. A broadcast receiver can register to an event and is notified if such an event is sent.

Your application can register to system events, e.g., a new email has arrived, system boot is complete or a phone call is received and react accordingly.

2. Data transfer between activities

2.1. Data transfer to the target component

An intent contains certain header data, e.g., the desired action, the type, etc. Optionally an intent can also contain additional data based on an instance of the Bundle class which can be retrieved from the intent via the getExtras() method.

You can also add data directly to the Bundle via the overloaded putExtra() methods of the Intent objects. Extras are key/value pairs. The key is always of type String . As value you can use the primitive data types ( int , float , …​) plus objects of type String , Bundle , Parcelable and Serializable .

The receiving component can access this information via the getAction() and getData() methods on the Intent object. This Intent object can be retrieved via the getIntent() method.

The component which receives the intent can use the getIntent().getExtras() method call to get the extra data. That is demonstrated in the following code snippet.

2.2. Retrieving result data from a sub-activity

An activity can be closed via the back button on the phone. In this case the finish() method is performed. If the activity was started with the startActivity(Intent) method call, the caller requires no result or feedback from the activity which now is closed.

If you start the activity with the startActivityForResult() method call, you expect feedback from the sub-activity. Once the sub-activity ends, the onActivityResult() method on the sub-activity is called and you can perform actions based on the result.

In the startActivityForResult() method call you can specify a result code to determine which activity you started. This result code is returned to you. The started activity can also set a result code which the caller can use to determine if the activity was canceled or not.

The sub-activity uses the finish() method to create a new intent and to put data into it. It also sets a result via the setResult() method call.

The following example code demonstrates how to trigger an intent with the startActivityForResult() method.

If you use the startActivityForResult() method, then the started activity is called a sub-activity.

If the sub-activity is finished, it can send data back to its caller via an Intent. This is done in the finish() method.

Once the sub-activity finishes, the onActivityResult() method in the calling activity is called.

3. Registering for intents via intent filters

Intents are used to signal to the Android system that a certain event has occurred. Intents often describe the action which should be performed and provide data upon which such an action should be done. For example, your application can start a browser component for a certain URL via an intent. This is demonstrated by the following example.

But how does the Android system identify the components which can react to a certain intent?

A component can register itself via an intent filter for a specific action and specific data. An intent filter specifies the types of intents to which an activity, service, or broadcast receiver can respond to by declaring the capabilities of a component.

Android components register intent filters either statically in the AndroidManifest.xml or in case of a broadcast receiver also dynamically via code. An intent filter is defined by its category, action and data filters. It can also contain additional meta-data.

If an intent is sent to the Android system, the Android platform runs a receiver determination. It uses the data included in the intent. If several components have registered for the same intent filter, the user can decide which component should be started.

You can register your Android components via intent filters for certain events. If a component does not define one, it can only be called by explicit intents. This chapter gives an example for registering a component for an intent. The key for this registration is that your component registers for the correct action, mime-type and specifies the correct meta-data.

If you send such an intent to your system, the Android system determines all registered Android components for this intent. If several components have registered for this intent, the user can select which one should be used.

3.1. Example: Register an activity as browser

The following code will register an Activity for the Intent which is triggered when someone wants to open a webpage.

3.2. Example: Register an activity for the share intent

The following example registers an activity for the ACTION_SEND intent. It declares itself only relevant for the text/plain mime type.

If a component does not define an intent filter, it can only be called by explicit intents.

4. Pre-requistes for the following exercise

The following exercise demonstrates the usage of intents to start a sub-activities and how exchange data between them. It assume that you are either capable of creating activities or that you have finished the exercise described in https://www.vogella.com/tutorials/Android/article.html#exercise_first_ui_interface.

5. Exercise: Activity communication with intents

5.1. Create project and main layout

Create or reuse a new Android project with the com.vogella.android.testapp package. This application has an activity called CreateUserActivity .

5.2. Create data model

Create a new class named User that takes the provided name and gender.

5.3. Create a new layout file

Create a new layout file called activity_user_overview.xml which allows to display the data of a user.

The following screenshot can be used a inspiration.

For the following layout, only the text widget labeled Practice and the text widget for the user name is used. Feel free to reduce the layout to this.

The very simplified layout file of this activity might look like the following.

5.4. Create additional activity

Create a new class called UserOverviewActivity based on the following example code.

Add the new activity to the AndroidManifest.xml file. Ensure that this is the main entry point for the user (via the intent-filter). The CreateUserActivity activity cannot be started anymore by the user directly.

5.5. Start sub-activity providing some data

If your application is started, start the CreateUserActivity via the startActivityForResult method call.

In the finished version of the app, you would of course persists the user and reload it. In this case the create user activity would only be started if no user was found.

The following code gives some pointers on how to solve this. Solve the TODO’s in the source code so that the activity is started from the onClick() method.

5.6. Return the user data from the CreateUserActivity to the OverviewActivity

Return the selected data to the OverviewActivity .

5.7. Add LearnActivity activity to your application

Add another activity called LearnActivity to your application. This activity should allow to practice some math. Use the following screenshot as inspiration and build a similar user interface.

In Android you frequently add the implementing class as callback class. This can be useful if you have lots of buttons. For example, to register your activity as callback for the view, you can use the following snippet.

5.8. Allow to start the learning activity

Allow to start this activity from the UserOverviewActivity via the Practice text view.

Pass the user name and its current skillPoints as extra data to it. In the learn activity get the Bundle with the intent data via the getIntent().getExtras() method call. Get the value of the passed extra with the extras.getString(key) and extras.getInt(key) method on the bundle object.

5.9. Return data from LearnActivity

Transfer data back from your LearnActivity to the UserOverviewActivity once the user selects the Back button. Once finished return the new skillPoints to the calling application.

For this, implement the finish() method in the LearnActivity class.

A very simple version of this logic can be found in the following code.

5.10. Show the new skill data in the OverviewActivity

If the skillPoints have increase by 10 points, show a Toast from the UserOverviewActivity to the user with a positive message.

Use the startActivityForResult() method in OverviewActivity to start the sub-activity. This allows you to use the onActivityResult() method to receive data from the sub-activity. Extract the extra data with the received bundle.

Show a Toast with the extra data to validate that you correctly received it. The following code contains some pointer on how to solve that.

5.11. Validate

Create a user in your application and start the training. Return to the overview application and start the training again. Return again to the overview application. The skillpoints displayed in the Toast should increase with each training.

6. Exercise: Using the share intent

Continue to use the applicatin from the previous exercise.

Obviously, you need a way to share you skills with your friends in your favorite social network.

Extend the layout of your activity with another button. A click on this Button should allow to share the value of the current skillPoints . The value for sending data via other applications is defined via the Intent.ACTION_SEND constant. To share data, create a new method called public void shareData(View view) based on the following snippet in your activity.

Connect this method with a new button via the android:onClick property in your layout. Run this application and select your button.

On the Android emulator it might be that only one application has registered for the intent and is started directly.

7. Exercise: Picking an image via an intent

The following exercise demonstrates picking an image from any registered photo application on Android via an intent.

7.1. Create project

Create a new Android project with the package name com.vogella.android.imagepick and one activity called ImagePickActivity.

Add an ImageView to hold an photo of the user to your MainActivity .

Change your activity class according to the following coding.

7.2. Validate

If you run this application, you can select an image from your image library on your Android phone and assign it to your ImageView .

8. Exercise: Register an activity as browser

8.1. Target

In the following exercise you register an activity as browser. This means, if an intent is triggered when someone wants to view an URL starting with http , your activity will be available to process this intent.

The example activity downloads the HTML source of this page and displays it in a TextView .

8.2. Create project

Create an Android project with the package name com.vogella.android.intent.browserfilter and an activity called BrowserActivity .

8.3. Register activity as browser

Register your activity to the Intent.Action_VIEW action and the scheme «http» via the following changes in your AndroidManifest.xml file. Ensure that your manifest also declares the permission to access the Internet.

Change the corresponding layout file according to the following listing.

Change your activity class to the following code.

8.4. Validate

Install your application. For this you need to configure Android Studio that you do not have a default activity.

If you trigger an intent to open an URL, the user should be able to select your custom browser implementation. Trigger for this purpose the following intent from one of your Android applications by adding for example an additional button to the application which can trigger the code.

If you select your component, the HTML code is loaded and displayed into your TextView .

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