基于WPF實現跳動的字符效果

更新時間：2023年08月10日 08:43:18 作者：czwy

這篇文章主要和大家介紹一個好玩但實際作用可能不太大的動畫效果：跳動的字符，本文將利用WPF實現這一效果，感興趣的小伙伴可以學習一下

本文將介紹一個好玩但實際作用可能不太大的動畫效果：跳動的字符。為了提高動畫效果的可重用性以及調用的靈活性，通過Behavior實現跳動的字符動畫。先看下效果：

技術要點與實現

通過TextEffect的PositionStart和PositionCount屬性控制應用動畫效果的子字符串的起始位置以及長度，同時使用TranslateTransform設置字符縱坐標的移動變換，以實現跳動的效果。主要步驟如下：

在OnAttached方法中，注冊Loaded事件，在Load事件中為TextBlock添加TextEffect效果，其中PositionCount設置為1，每次只跳動一個字符。
添加啟動動畫效果的BeginEffect方法，并創(chuàng)建控制子字符縱向移動變換的線性動畫。然后根據字符串（剔除空字符）的長度n，創(chuàng)建n個關鍵幀，每個關鍵幀中把PositionStart設置為要跳動的字符在字符串中的索引
在開啟動畫屬性IsEnabled=true和TextBlock內容變化時,啟動動畫效果

在創(chuàng)建關鍵幀設置跳動字符位置時剔除了空字符，是為了是動畫效果顯得連貫

public class DanceCharEffectBehavior : Behavior<TextBlock>
    {
        private TextEffect _textEffect;
        private string _textEffectName;
        private TranslateTransform _translateTransform = null;
        private string _translateTransformName;
        private Storyboard _storyboard;
        protected override void OnAttached()
        {
            base.OnAttached();
            this.AssociatedObject.Loaded += AssociatedObject_Loaded;
            this.AssociatedObject.Unloaded += AssociatedObject_Unloaded;
            this.AssociatedObject.IsVisibleChanged += AssociatedObject_IsVisibleChanged;
            BindingOperations.SetBinding(this, DanceCharEffectBehavior.InternalTextProperty, new Binding("Text") { Source = this.AssociatedObject });
        }
        protected override void OnDetaching()
        {
            base.OnDetaching();
            this.AssociatedObject.Loaded -= AssociatedObject_Loaded;
            this.AssociatedObject.Unloaded -= AssociatedObject_Unloaded;
            this.AssociatedObject.IsVisibleChanged -= AssociatedObject_IsVisibleChanged;
            this.ClearValue(DanceCharEffectBehavior.InternalTextProperty);
            if (_storyboard != null)
            {
                _storyboard.Remove(this.AssociatedObject);
                _storyboard.Children.Clear();
            }
            if (_textEffect != null)
                this.AssociatedObject.TextEffects.Remove(_textEffect);
        }
        private void AssociatedObject_IsVisibleChanged(object sender, DependencyPropertyChangedEventArgs e)
        {
            if ((bool)e.NewValue == false)
            {
                if (_storyboard != null)
                    _storyboard.Stop(this.AssociatedObject);
            }
            else
            {
                BeginEffect(this.AssociatedObject.Text);
            }
        }
        private void AssociatedObject_Loaded(object sender, RoutedEventArgs e)
        {
            if (_textEffect == null)
            {
                this.AssociatedObject.TextEffects.Add(_textEffect = new TextEffect()
                {
                    PositionCount = 1,
                    Transform = _translateTransform = new TranslateTransform(),
                });
                NameScope.SetNameScope(this.AssociatedObject, new NameScope());
                this.AssociatedObject.RegisterName(_textEffectName = "n" + Guid.NewGuid().ToString("N"), _textEffect);
                this.AssociatedObject.RegisterName(_translateTransformName = "n" + Guid.NewGuid().ToString("N"), _translateTransform);
                if (IsEnabled)
                    BeginEffect(this.AssociatedObject.Text);
            }
        }
        private void AssociatedObject_Unloaded(object sender, RoutedEventArgs e)
        {
            StopEffect();
        }
        private void SetEffect(string text)
        {
            if (string.IsNullOrEmpty(text) || this.AssociatedObject.IsLoaded == false)
            {
                StopEffect();
                return;
            }
            BeginEffect(text);
        }
        private void StopEffect()
        {
            if (_storyboard != null)
            {
                _storyboard.Stop(this.AssociatedObject);
            }
        }
        private void BeginEffect(string text)
        {
            StopEffect();
            int textLength = text.Length;
            if (textLength < 1 || _translateTransformName == null || IsEnabled == false) return;
            if (_storyboard == null)
                _storyboard = new Storyboard();
            double duration = 0.5d;
            DoubleAnimation da = new DoubleAnimation();
            Storyboard.SetTargetName(da, _translateTransformName);
            Storyboard.SetTargetProperty(da, new PropertyPath(TranslateTransform.YProperty));
            da.From = 0d;
            da.To = 10d;
            da.Duration = TimeSpan.FromSeconds(duration / 2d);
            da.RepeatBehavior = RepeatBehavior.Forever;
            da.AutoReverse = true;
            char emptyChar = ' ';
            List<int> lsb = new List<int>();
            for (int i = 0; i < textLength; ++i)
            {
                if (text[i] != emptyChar)
                {
                    lsb.Add(i);
                }
            }
            Int32AnimationUsingKeyFrames frames = new Int32AnimationUsingKeyFrames();
            Storyboard.SetTargetName(frames, _textEffectName);
            Storyboard.SetTargetProperty(frames, new PropertyPath(TextEffect.PositionStartProperty));
            frames.Duration = TimeSpan.FromSeconds((lsb.Count) * duration);
            frames.RepeatBehavior = RepeatBehavior.Forever;
            frames.AutoReverse = true;
            int ii = 0;
            foreach (int index in lsb)
            {
                frames.KeyFrames.Add(new DiscreteInt32KeyFrame()
                {
                    Value = index,
                    KeyTime = TimeSpan.FromSeconds(ii * duration),
                });
                ++ii;
            }
            _storyboard.Children.Add(da);
            _storyboard.Children.Add(frames);
            _storyboard.Begin(this.AssociatedObject, true);
        }
        private string InternalText
        {
            get { return (string)GetValue(InternalTextProperty); }
            set { SetValue(InternalTextProperty, value); }
        }
        private static readonly DependencyProperty InternalTextProperty =
        DependencyProperty.Register("InternalText", typeof(string), typeof(DanceCharEffectBehavior),
        new PropertyMetadata(OnInternalTextChanged));
        private static void OnInternalTextChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            var source = d as DanceCharEffectBehavior;
            if (source._storyboard != null)
            {
                source._storyboard.Stop(source.AssociatedObject);
                source._storyboard.Children.Clear();
            }
            source.SetEffect(e.NewValue == null ? string.Empty : e.NewValue.ToString());
        }
        public bool IsEnabled
        {
            get { return (bool)GetValue(IsEnabledProperty); }
            set { SetValue(IsEnabledProperty, value); }
        }
        public static readonly DependencyProperty IsEnabledProperty =
            DependencyProperty.Register("IsEnabled", typeof(bool), typeof(DanceCharEffectBehavior), new PropertyMetadata(true, (d, e) =>
            {
                bool b = (bool)e.NewValue;
                var source = d as DanceCharEffectBehavior;
                source.SetEffect(source.InternalText);
            }));
    }

調用的時候只需要在TextBlock添加Behavior即可，代碼如下

<TextBlock FontSize="20" Text="Hello">
    <i:Interaction.Behaviors>
        <local:DanceCharEffectBehavior x:Name="titleEffect" IsEnabled="True" />
    </i:Interaction.Behaviors>
</TextBlock>

結尾

本例中還有許多可以完善的地方，比如字符跳動的幅度可以根據實際的FontSize來設置，或者增加依賴屬性來控制；動畫是否倒退播放，是否循環(huán)播放，以及動畫的速度都可以通過增加依賴屬性在調用時靈活設置。

到此這篇關于基于WPF實現跳動的字符效果的文章就介紹到這了,更多相關WPF字符跳動效果內容請搜索腳本之家以前的文章或繼續(xù)瀏覽下面的相關文章希望大家以后多多支持腳本之家！

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