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Part of https://github.com/flutter/flutter/issues/145009 This is part one of the wiki migration. This moves all wiki pages wholesale into the new docs directory with no changes. Follow up PRs will sort them, updating breadcrumbs and links.
119 lines
3.2 KiB
Markdown
119 lines
3.2 KiB
Markdown
_**Everything in this doc and linked from this doc is experimental. These details WILL change. Do not use these instructions or APIs in production code because we will break you.**_
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# Launch Flutter with non-main entrypoint
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Typically, a Flutter app begins execution at the Dart method called `main()`, however this is not required. Developers can specify a different Dart entrypoint:
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## FlutterActivity
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Two options are available to specify a non-standard Dart entrypoint for a `FlutterActivity`.
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### Option 1: AndroidManifest.xml meta-data
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Specify your desired Dart entrypoint as `meta-data` in your `AndroidManifest.xml`:
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```xml
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<application ...>
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<activity
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android:name="io.flutter.embedding.android.FlutterActivity"
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...
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>
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<meta-data
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android:name="io.flutter.Entrypoint"
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android:value="myMainDartMethod"
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/>
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</activity>
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</application>
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```
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Option 2: Subclass `FlutterActivity` and override a method
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Override the `getDartEntrypointFunctionName()` method:
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```java
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public class MyFlutterActivity extends FlutterActivity {
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@Override
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@NonNull
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public String getDartEntrypointFunctionName() {
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return "myMainDartMethod";
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}
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}
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```
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## FlutterFragment
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Two options are available to specify a non-standard Dart entrypoint for a `FlutterFragment`.
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### Option 1: Use FlutterFragmentBuilder
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```java
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// Example for a FlutterFragment that creates its own FlutterEngine.
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//
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// Note: a Dart entrypoint cannot be set when using a cached engine because the
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// cached engine has already started executing Dart.
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FlutterFragment flutterFragment = new FlutterFragment
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.withNewEngine()
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.dartEntrypoint("myMainDartMethod")
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.build();
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```
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### Option 2: Subclass FlutterFragment
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```java
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public class MyFlutterFragment extends FlutterFragment {
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@Override
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@NonNull
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public String getDartEntrypointFunctionName() {
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return "myMainDartMethod";
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}
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}
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```
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## FlutterEngine
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When manually initializing a `FlutterEngine`, you take on the responsibility of
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invoking the desired Dart entrypoint, even if you want the standard `main()` method.
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The following examples illustrate how to execute a Dart entrypoint with a
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`FlutterEngine`.
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Example using standard entrypoint:
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```java
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// Instantiate a new FlutterEngine.
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FlutterEngine flutterEngine = new FlutterEngine(context);
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// Start executing Dart using a default entrypoint, which resolves to "main()".
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flutterEngine
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.getDartExecutor()
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.executeDartEntrypoint(
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DartEntrypoint.createDefault();
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);
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```
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Example using custom entrypoint:
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```java
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// Instantiate a new FlutterEngine.
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FlutterEngine flutterEngine = new FlutterEngine(context);
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// Start executing Dart using a custom entrypoint.
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flutterEngine
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.getDartExecutor()
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.executeDartEntrypoint(
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new DartEntrypoint(
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FlutterMain.findAppBundlePath(),
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"myMainDartMethod"
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)
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);
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```
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# Avoid Tree Shaking in Release
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When you build in release mode, your Dart code is tree-shaken. This means that the compiler removes any Dart code that it thinks you're not using. This includes your special entrypoints. To avoid crashing in release mode as a result of tree-shaking, be sure to place the following `@pragma` above each of your custom entrypoints.
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```dart
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@pragma('vm:entry-point')
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void myMainDartMethod() {
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// implementation
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}
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``` |