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Avoid exceptions for control flow (#46897)

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This commit is contained in:
Dan Field 2019-12-12 16:53:01 -05:00 committed by Flutter GitHub Bot
parent a467932d5b
commit 948e2b0101
2 changed files with 28 additions and 17 deletions
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36
packages/flutter/lib/src/services/platform_channel.dart
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@ -140,6 +140,22 @@ class MethodChannel {
BinaryMessenger get binaryMessenger => _binaryMessenger ?? defaultBinaryMessenger; // ignore: deprecated_member_use_from_same_package
final BinaryMessenger _binaryMessenger;
@optionalTypeArgs
Future<T> _invokeMethod<T>(String method, { bool missingOk, dynamic arguments }) async {
assert(method != null);
final ByteData result = await binaryMessenger.send(
name,
codec.encodeMethodCall(MethodCall(method, arguments)),
);
if (result == null) {
if (missingOk) {
return null;
}
throw MissingPluginException('No implementation found for method $method on channel $name');
}
return codec.decodeEnvelope(result) as T;
}
/// Invokes a [method] on this channel with the specified [arguments].
///
/// The static type of [arguments] is `dynamic`, but only values supported by
@ -309,17 +325,8 @@ class MethodChannel {
/// * <https://api.flutter.dev/javadoc/io/flutter/plugin/common/MethodCall.html>
/// for how to access method call arguments on Android.
@optionalTypeArgs
Future<T> invokeMethod<T>(String method, [ dynamic arguments ]) async {
assert(method != null);
final ByteData result = await binaryMessenger.send(
name,
codec.encodeMethodCall(MethodCall(method, arguments)),
);
if (result == null) {
throw MissingPluginException('No implementation found for method $method on channel $name');
}
final T typedResult = codec.decodeEnvelope(result) as T;
return typedResult;
Future<T> invokeMethod<T>(String method, [ dynamic arguments ]) {
return _invokeMethod<T>(method, missingOk: false, arguments: arguments);
}
/// An implementation of [invokeMethod] that can return typed lists.
@ -425,12 +432,7 @@ class OptionalMethodChannel extends MethodChannel {
@override
Future<T> invokeMethod<T>(String method, [ dynamic arguments ]) async {
try {
final T result = await super.invokeMethod<T>(method, arguments);
return result;
} on MissingPluginException {
return null;
}
return super._invokeMethod<T>(method, missingOk: true, arguments: arguments);
}
@override

9
packages/flutter/test/services/platform_channel_test.dart
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@ -42,6 +42,7 @@ void main() {
const MessageCodec<dynamic> jsonMessage = JSONMessageCodec();
const MethodCodec jsonMethod = JSONMethodCodec();
const MethodChannel channel = MethodChannel('ch7', jsonMethod);
const OptionalMethodChannel optionalMethodChannel = OptionalMethodChannel('ch8', jsonMethod);
test('can invoke method and get result', () async {
ServicesBinding.instance.defaultBinaryMessenger.setMockMessageHandler(
'ch7',
@ -157,6 +158,14 @@ void main() {
fail('MissingPluginException expected');
}
});
test('can invoke unimplemented method (optional)', () async {
ServicesBinding.instance.defaultBinaryMessenger.setMockMessageHandler(
'ch8',
(ByteData message) async => null,
);
final String result = await optionalMethodChannel.invokeMethod<String>('sayHello', 'hello');
expect(result, isNull);
});
test('can handle method call with no registered plugin', () async {
channel.setMethodCallHandler(null);
final ByteData call = jsonMethod.encodeMethodCall(const MethodCall('sayHello', 'hello'));