3月Flutter小报｜读小报涨常识

以allMessagesHandler利用举例，如果我们有这样一个MethodChannel

class PipeLinePlugin { PipeLinePlugin({this.pipeLineId, this.onTextureRegistered}) { _channel = MethodChannel('method_channel/pipeline_$pipeLineId');/// 调用start后，Platform会回调registerTextureId _channel.setMethodCallHandler((call) {if (call.method == 'registerTextureId' && call.arguments is Map) {int textureId = (call.arguments as Map)?['textureId']; onTextureRegistered?.call(textureId); } }); }final String pipeLineId;final MethodChannel _channel;final Function(int textureId)? onTextureRegistered; Future<bool?> start() async {final bool? result = await _channel.invokeMethod('start', <String, dynamic>{'id': pipeLineId}) as bool?;return result; } Future<bool?> stop() async {final bool? result = await _channel.invokeMethod('stop', <String, dynamic>{'id': pipeLineId}) as bool?;return result; }}

我们可以这样Mock它，然后我们的测试用例就能正常实行了。

const StandardMethodCodec methodCodec = StandardMethodCodec();/// 如果channel名字是按规则天生的，可以拦截所有的MethodChannel，再从中找到你须要Mock的MethodChannelmessenger.allMessagesHandler = (String channel, MessageHandler? handler, ByteData? message) async {final MethodCall call = methodCodec.decodeMethodCall(message);if (channel.startWith('method_channel/pipeline')) {if (call.method == 'start') {/// Platform收到start后，须要回调registerTextureIdfinal platformResultCall = MethodCall('registerTextureId', {'textureId': 0}); messenger.handlePlatformMessage(channel, methodCodec.encodeMethodCall(platformResultCall), ); } }/// Flutter的MethodCall统一返回truereturn methodCodec.encodeSuccessEnvelope(true);}Flutter如何获取键盘的完全高度

我们知道在Flutter中获取键盘高度可以通过向WidgetsBinding注册监听，当键盘弹出或消逝时会回调didChangeMetrics方法。
须要把稳的是，在Flutter3新增IOS键盘动画后，IOS会和Android一样回调didChangeMetrics多次，并且每次回调中MediaQueryData.fromWindow(window).viewInsets.bottom的值都是此时键盘冒出来的高度，即键盘实时高度。
如果我们想获取键盘的完全高度，只须要一贯取和上次比较的最大值，然后保存下来就可以了。

/// Flutter3 /// 获取键盘高度@overridevoid didChangeMetrics() {final bottom = MediaQueryData.fromWindow(window).viewInsets.bottom;// 键盘存在中间态，回调是键盘冒出来的高度 keyboardHeight = max(keyboardHeight, bottom);if (bottom == 0) { isKeyboardShow = false; } else if (bottom == keyboardHeight || keyboardHeight == 0) { isKeyboardShow = true; } else { isKeyboardShow = ; }// 键盘完备收起或展开再刷新页面if (isKeyboardShow != && _preKeyboardShow != isKeyboardShow) { _keyboardStateNotifier.notifyListeners(); }if (bottom < keyboardHeight) { _sp?.setDouble(KEYBOARD_MAX_HEIGHT, keyboardHeight); }}/// Flutter3之前，获取键盘高度@overridevoid didChangeMetrics() {final bottom = MediaQueryData.fromWindow(window).viewInsets.bottom;/// ios点击键盘表情时，键盘高度会增加，后面点拼音后也回不到这个高度了if (Platform.isIOS) {/// ios键盘有两种高度，但不存在中间态，回调便是键盘高度 isKeyboardShow = bottom > 0;if (isKeyboardShow) { keyboardHeight = bottom; } } else {/// Android键盘存在中间态，回调是键盘冒出来的高度 keyboardHeight = max(keyboardHeight, bottom);if (bottom == 0) { isKeyboardShow = false; } else if (bottom == keyboardHeight || keyboardHeight == 0) { isKeyboardShow = true; } else { isKeyboardShow = ; } }// 键盘完备收起或展开再刷新页面if (isKeyboardShow != && _preKeyboardShow != isKeyboardShow) { _keyboardStateNotifier.notifyListeners(); }if (bottom < keyboardHeight) { _sp?.setDouble(KEYBOARD_MAX_HEIGHT, keyboardHeight); }}

例如我们想在键盘上做一个输入框，只须要给输入框底部添加一个和键盘实时高度相同的Padding，就能做到像Scaffold#bottomSheet一样跟随键盘动画的效果了