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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.
Launch Flutter with non-main entrypoint
Typically, a Flutter app begins execution at the Dart method called main()
, however this is not required. Developers can specify a different Dart entrypoint:
FlutterActivity
Two options are available to specify a non-standard Dart entrypoint for a FlutterActivity
.
Option 1: AndroidManifest.xml meta-data
Specify your desired Dart entrypoint as meta-data
in your AndroidManifest.xml
:
xml
<application ...>
<activity
android:name="io.flutter.embedding.android.FlutterActivity"
...
>
<meta-data
android:name="io.flutter.Entrypoint"
android:value="myMainDartMethod"
/>
</activity>
</application>
Option 2: Subclass FlutterActivity
and override a method
Override the getDartEntrypointFunctionName()
method:
java
public class MyFlutterActivity extends FlutterActivity {
@Override
@NonNull
public String getDartEntrypointFunctionName() {
return "myMainDartMethod";
}
}
FlutterFragment
Two options are available to specify a non-standard Dart entrypoint for a FlutterFragment
.
Option 1: Use FlutterFragmentBuilder
java
// Example for a FlutterFragment that creates its own FlutterEngine.
//
// Note: a Dart entrypoint cannot be set when using a cached engine because the
// cached engine has already started executing Dart.
FlutterFragment flutterFragment = new FlutterFragment
.withNewEngine()
.dartEntrypoint("myMainDartMethod")
.build();
Option 2: Subclass FlutterFragment
java
public class MyFlutterFragment extends FlutterFragment {
@Override
@NonNull
public String getDartEntrypointFunctionName() {
return "myMainDartMethod";
}
}
FlutterEngine
When manually initializing a FlutterEngine
, you take on the responsibility of invoking the desired Dart entrypoint, even if you want the standard main()
method. The following examples illustrate how to execute a Dart entrypoint with a FlutterEngine
.
Example using standard entrypoint:
java
// Instantiate a new FlutterEngine.
FlutterEngine flutterEngine = new FlutterEngine(context);
// Start executing Dart using a default entrypoint, which resolves to "main()".
flutterEngine
.getDartExecutor()
.executeDartEntrypoint(
DartEntrypoint.createDefault();
);
Example using custom entrypoint:
java
// Instantiate a new FlutterEngine.
FlutterEngine flutterEngine = new FlutterEngine(context);
// Start executing Dart using a custom entrypoint.
flutterEngine
.getDartExecutor()
.executeDartEntrypoint(
new DartEntrypoint(
FlutterMain.findAppBundlePath(),
"myMainDartMethod"
)
);
Avoid Tree Shaking in Release
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.
dart
@pragma('vm:entry-point')
void myMainDartMethod() {
// implementation
}