Starting another activity by Android Developers<\/h2>\n\n\n\n
Let’s assume that in A<\/em><\/span>ndroid application<\/span><\/em> we have created a list of projects from which we can access the details of a selected project. After selecting the element showing the list of projects, we go on to view its details. If we write this navigation in the same way as the guide shows it, it would look like the following example:<\/span><\/p>\n\n\n\n The guide has done its job. It shows navigation between activities in a way that is accessible to the reader. Problems may appear only after the application has grown.<\/span><\/p>\n\n\n\n When the application grows, it will be difficult to maintain such code. <\/span><\/p>\n\n\n\n To start with, let’s define the main problems:<\/span><\/p>\n\n\n\n How can we improve the above approach?<\/p>\n\n\n\n Let\u2019s ask some questions and try to find an answer to them:<\/p>\n\n\n\n How can you unify data transfer between activities?<\/b><\/p>\n\n\n\n How can we unify the method for creating intentions and starting activities?<\/b><\/p>\n\n\n\n How can we unify the method for receiving data from an intention?<\/b><\/p>\n\n\n\n In the following part of the<\/b> <\/span>“Android<\/strong> tutorial:<\/b> starting another activity<\/strong>“<\/span>, let’s try to go through some solutions to the difficulties described above.<\/span><\/p>\n\n\n\n Incomplete data transfer between activities, building intentions and starting activities and receiving data from intentions. The following solutions show how you can deal with these problems during A<\/em><\/span>ndroid app development<\/span>.<\/span><\/em><\/p>\n\n\n\n To fix this problem, we will create a model that will store all the required data. In order the whole thing to make sense, it should be given a single form. That’s why I wrote the It is an open class, so we are able to inherit from it and use it in generic arguments. It contains its own identifier and is marked with the parcelize annotation. The parcelize annotation comes from <\/span>Kotlin Android extensions<\/span><\/a>. For a class with this annotation, an implementation of the <\/span>parcelable<\/span><\/a> interface will be generated, thanks to which, we gain the ability to move data in intentions as parcelable using the <\/span>putParcelable<\/span><\/a> method. <\/span><\/p>\n\n\n\n The nested empty class will serve us as the default empty value of the For each activity, we write a class that contains all the necessary data (even if it is only one field).<\/span> Now we can go on to solve the next problem. We need to unify the method for creating intentions and starting activities. For that we’ll use <\/span>higher-order functions<\/span><\/a> and <\/span>extension functions<\/span><\/a>. <\/span>Creating intentions:<\/span><\/p>\n\n\n\n This function is an extension for the We are able to create intentions in a uniform way throughout the application.<\/p>\n\n\n\n To solve our aforementioned problem, we need to write a function that will start an activity with a defined Which looks like this:<\/p>\n\n\n\n In its design, it closely resembles the Our last problem is the unification of receiving data from intentions. You can do it in many ways, but we will again use extension functions.<\/p>\n\n\n\n This function shortens the writing and improves its readability. We have solved the defined problem!<\/p>\n\n\n\n We already have all the necessary elements to our puzzle. So we can put them together to see the final result.<\/p>\n\n\n\n Let\u2019s see if we can correct the example from the beginning of the article.<\/p>\n\n\n\nconst val EXTRA_PROJECT_ID = \"com.gratitude.ProjectId\"\nconst val EXTRA_PROJECT_NAME = \"com.gratitude.ProjectName\"\nconst val EXTRA_PROJECT_BACKGROUND_IMAGE_URL = \"com.gratitude.ProjectBackgroundImageUrl\"\n\nclass ProjectsActivity : AppCompatActivity() {\n override fun onCreate(savedInstanceState: Bundle?) {\n super.onCreate(savedInstanceState)\n setContentView(R.layout.activity_projects)\n }\n\n fun showProjectDetails(project: Project) {\n val intent = Intent(this, ProjectDetailsActivity::class.java).apply {\n putExtra(EXTRA_PROJECT_ID, project.id)\n putExtra(EXTRA_PROJECT_NAME, project.name)\n putExtra(\n EXTRA_PROJECT_BACKGROUND_IMAGE_URL,\n project.backgroundImageUrl\n )\n }\n startActivity(intent)\n }\n}\n\noverride fun onCreate(savedInstanceState: Bundle?) {\n super.onCreate(savedInstanceState)\n setContentView(R.layout.activity_project_details)\n \n val id = intent.getStringExtra(EXTRA_PROJECT_ID)\n val name = intent.getStringExtra(EXTRA_PROJECT_NAME)\n val imageUrl = intent.getStringExtra(EXTRA_PROJECT_BACKGROUND_IMAGE_URL)\n \n val projectNameTextView = findViewById(R.id.projectNametextView)\n .apply {\n text = name\n }\n}<\/code><\/pre>\n\n\n\nAndroid app development: detected problems<\/h3>\n\n\n\n
![\"Android](\"https:\/\/zaven.co\/blog\/wp-content\/uploads\/2019\/01\/Depositphotos_49607661_l-2015-730x730.jpg\")
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<\/span><\/li><\/ul>\n\n\n\nAndroid app development: the solutions<\/h2>\n\n\n\n
Android tutorial<\/b>: how to unify data transfer between activities?<\/b><\/h3>\n\n\n\n
NavigationBundle<\/code> base model.<\/span><\/p>\n\n\n\n@Parcelize\nopen class NavigationBundle(val uuid: UUID = UUID.randomUUID())\n : Parcelable {\n class Empty : NavigationBundle()\n}<\/code><\/pre>\n\n\n\nNavigationBundle<\/code>. An example of the NavigationBundle<\/code>:<\/span><\/p>\n\n\n\nclass ProjectDetailsNavigationBundle(\n val projectId: UUID,\n val projectName: String,\n val projectBackgroundImageUrl: String\n) : NavigationBundle()<\/code><\/pre>\n\n\n\n<\/code><\/p>\n\n\n\nAndroid tutorial<\/b>: how can we unify the way of creating intentions and starting activities? <\/b><\/h3>\n\n\n\n
inline fun FragmentActivity.createIntent(\n bundle: NavigationBundle = NavigationBundle.Empty(),\n crossinline block: Intent.() -> Unit = {}\n): Intent {\n val intent = Intent(this, T::class.java)\n val extras = Bundle()\n extras.putParcelable(KEY_NAVIGATION_BUNDLE, bundle)\n intent.putExtras(extras)\n return intent.apply(block)\n}<\/code><\/pre>\n\n\n\nFragmentActivity<\/code> class and accepts three parameters:<\/p>\n\n\n\nNavigationBundle<\/code><\/li>NavigationBundle<\/code>.<\/p>\n\n\n\ninline fun FragmentActivity.beginActivity(\n bundle: NavigationBundle = NavigationBundle.Empty(),\n crossinline block: Intent.() -> Unit = {}\n) {\n val intent = this.createIntent(bundle, block)\n this.startActivity(intent)\n}<\/code><\/pre>\n\n\n\ncreateIntent<\/code> function, since it takes the same parameters. The difference is that this time we use the createIntent<\/code> function to create an intention, and then start the activity by calling the startActivity method<\/code>.<\/p>\n\n\n\nAndroid tutorial: how can we unify the method for receiving data from intention?<\/h3>\n\n\n\n
inline fun AppCompatActivity.getNavigationBundleOrNull(): T? {\n return intent.extras?.getParcelable(KEY_NAVIGATION_BUNDLE)\n}<\/code><\/pre>\n\n\n\nStarting another activity: revived<\/h2>\n\n\n\n
class ProjectsActivity : AppCompatActivity() {\n override fun onCreate(savedInstanceState: Bundle?) {\n super.onCreate(savedInstanceState)\n setContentView(R.layout.activity_projects)\n }\n\n \/** Called when the user taps the project item *\/\n fun showProjectDetails(project: Project) {\n val navigationBundle = ProjectDetailsNavigationBundle(\n project.id,\n project.name,\n project.backgroundImageUrl\n )\n beginActivity(navigationBundle)\n }\n}\n\noverride fun onCreate(savedInstanceState: Bundle?) {\n super.onCreate(savedInstanceState)\n setContentView(R.layout.activity_project_details)\n \n \/\/ Get the Intent that started this activity and extract the value\n val navigationBundle =\n getNavigationBundleOrNull()\n\n \n \/\/ Capture the layout's TextView and set the string as its text\n val projectNameTextView = findViewById(R.id.projectNametextView)\n .apply {\n text = navigationBundle?.projectName\n }\n}<\/code><\/pre>\n\n\n\nAndroid tutorial: starting another activity – summary<\/h2>\n\n\n\n