在 HTML5 canvas 中使用 Konva 进行文本编辑

用户无法直接编辑 Konva.Text 内容，原因有很多。实际上，canvas API 并不为此目的而设计。可以在 canvas 上模拟文本编辑（通过绘制闪烁光标、模拟选择等）。 Konva 并不支持这种情况。我们建议使用本地 DOM 元素（如 input 或 textarea）在 canvas 外部编辑用户输入。

如果您想启用完整的富文本编辑功能，请参见富文本演示。

说明：双击文本以编辑。输入内容。按 Enter 或点击外部以保存更改。

Vanilla
React
Vue

import Konva from 'konva';

Konva._fixTextRendering = true;

const stage = new Konva.Stage({
container: 'container',
width: window.innerWidth,
height: window.innerHeight,
});

const layer = new Konva.Layer();
stage.add(layer);

const textNode = new Konva.Text({
text: '一些文本',
x: 50,
y: 80,
fontSize: 20,
draggable: true,
width: 200,
});

layer.add(textNode);

const tr = new Konva.Transformer({
node: textNode,
enabledAnchors: ['middle-left', 'middle-right'],
boundBoxFunc: function (oldBox, newBox) {
newBox.width = Math.max(30, newBox.width);
return newBox;
},
});

textNode.on('transform', function () {
textNode.setAttrs({
width: textNode.width() * textNode.scaleX(),
scaleX: 1,
});
});

layer.add(tr);

textNode.on('dblclick dbltap', () => {
textNode.hide();
tr.hide();

const textPosition = textNode.absolutePosition();
const stageBox = stage.container().getBoundingClientRect();

const areaPosition = {
x: stageBox.left + textPosition.x,
y: stageBox.top + textPosition.y,
};

const textarea = document.createElement('textarea');
document.body.appendChild(textarea);

textarea.value = textNode.text();
textarea.style.position = 'absolute';
textarea.style.top = areaPosition.y + 'px';
textarea.style.left = areaPosition.x + 'px';
textarea.style.width = textNode.width() - textNode.padding() * 2 + 'px';
textarea.style.height = textNode.height() - textNode.padding() * 2 + 5 + 'px';
textarea.style.fontSize = textNode.fontSize() + 'px';
textarea.style.border = 'none';
textarea.style.padding = '0px';
textarea.style.margin = '0px';
textarea.style.overflow = 'hidden';
textarea.style.background = 'none';
textarea.style.outline = 'none';
textarea.style.resize = 'none';
textarea.style.lineHeight = textNode.lineHeight().toString();
textarea.style.fontFamily = textNode.fontFamily();
textarea.style.transformOrigin = 'left top';
textarea.style.textAlign = textNode.align();
textarea.style.color = textNode.fill().toString();

const rotation = textNode.rotation();
let transform = '';
if (rotation) {
transform += 'rotateZ(' + rotation + 'deg)';
}
transform += 'translateY(-' + 2 + 'px)';
textarea.style.transform = transform;

textarea.style.height = 'auto';
textarea.style.height = textarea.scrollHeight + 3 + 'px';

textarea.focus();

function removeTextarea() {
textarea.parentNode.removeChild(textarea);
window.removeEventListener('click', handleOutsideClick);
window.removeEventListener('touchstart', handleOutsideClick);
textNode.show();
tr.show();
tr.forceUpdate();
}

function setTextareaWidth(newWidth = 0) {
if (!newWidth) {
newWidth = textNode.placeholder.length * textNode.fontSize();
}
textarea.style.width = newWidth + 'px';
}

textarea.addEventListener('keydown', function (e) {
if (e.key === 'Enter' && !e.shiftKey) {
textNode.text(textarea.value);
removeTextarea();
}
if (e.key === 'Escape') {
removeTextarea();
}
});

textarea.addEventListener('keydown', function () {
const scale = textNode.getAbsoluteScale().x;
setTextareaWidth(textNode.width() * scale);
textarea.style.height = 'auto';
textarea.style.height = textarea.scrollHeight + textNode.fontSize() + 'px';
});

function handleOutsideClick(e) {
if (e.target !== textarea) {
textNode.text(textarea.value);
removeTextarea();
}
}
setTimeout(() => {
window.addEventListener('click', handleOutsideClick);
});
});

Open Sandbox

import { Stage, Layer, Text, Transformer } from 'react-konva';
import { Html } from 'react-konva-utils';
import { useEffect, useRef, useState, useCallback } from 'react';

Konva._fixTextRendering = true;

const TextEditor = ({ textNode, onClose, onChange }) => {
  const textareaRef = useRef(null);

  useEffect(() => {
    if (!textareaRef.current) return;

    const textarea = textareaRef.current;
    const stage = textNode.getStage();
    const textPosition = textNode.position();
    const stageBox = stage.container().getBoundingClientRect();
    const areaPosition = {
      x: textPosition.x,
      y: textPosition.y,
    };

    // 匹配文本节点的样式
    textarea.value = textNode.text();
    textarea.style.position = 'absolute';
    textarea.style.top = `${areaPosition.y}px`;
    textarea.style.left = `${areaPosition.x}px`;
    textarea.style.width = `${textNode.width() - textNode.padding() * 2}px`;
    textarea.style.height = `${textNode.height() - textNode.padding() * 2 + 5}px`;
    textarea.style.fontSize = `${textNode.fontSize()}px`;
    textarea.style.border = 'none';
    textarea.style.padding = '0px';
    textarea.style.margin = '0px';
    textarea.style.overflow = 'hidden';
    textarea.style.background = 'none';
    textarea.style.outline = 'none';
    textarea.style.resize = 'none';
    textarea.style.lineHeight = textNode.lineHeight();
    textarea.style.fontFamily = textNode.fontFamily();
    textarea.style.transformOrigin = 'left top';
    textarea.style.textAlign = textNode.align();
    textarea.style.color = textNode.fill();

    const rotation = textNode.rotation();
    let transform = '';
    if (rotation) {
      transform += `rotateZ(${rotation}deg)`;
    }
    textarea.style.transform = transform;

    textarea.style.height = 'auto';
    textarea.style.height = `${textarea.scrollHeight + 3}px`;

    textarea.focus();

    const handleOutsideClick = (e) => {
      if (e.target !== textarea) {
        onChange(textarea.value);
        onClose();
      }
    };

    // 添加事件监听器
    const handleKeyDown = (e) => {
      if (e.key === 'Enter' && !e.shiftKey) {
        e.preventDefault();
        onChange(textarea.value);
        onClose();
      }
      if (e.key === 'Escape') {
        onClose();
      }
    };

    const handleInput = () => {
      const scale = textNode.getAbsoluteScale().x;
      textarea.style.width = `${textNode.width() * scale}px`;
      textarea.style.height = 'auto';
      textarea.style.height = `${textarea.scrollHeight + textNode.fontSize()}px`;
    };

    textarea.addEventListener('keydown', handleKeyDown);
    textarea.addEventListener('input', handleInput);
    setTimeout(() => {
      window.addEventListener('click', handleOutsideClick);
    });

    return () => {
      textarea.removeEventListener('keydown', handleKeyDown);
      textarea.removeEventListener('input', handleInput);
      window.removeEventListener('click', handleOutsideClick);
    };
  }, [textNode, onChange, onClose]);

  return (
    <Html>
      <textarea
        ref={textareaRef}
        style={{
          minHeight: '1em',
          position: 'absolute',
        }}
      />
    </Html>
  );
};

const EditableText = () => {
  const [text, setText] = useState('一些文本');
  const [isEditing, setIsEditing] = useState(false);
  const [textWidth, setTextWidth] = useState(200);
  const textRef = useRef();
  const trRef = useRef();

  useEffect(() => {
    if (trRef.current && textRef.current) {
      trRef.current.nodes([textRef.current]);
    }
  }, [isEditing]);

  const handleTextDblClick = useCallback(() => {
    setIsEditing(true);
  }, []);

  const handleTextChange = useCallback((newText) => {
    setText(newText);
  }, []);

  const handleTransform = useCallback((e) => {
    const node = textRef.current;
    const scaleX = node.scaleX();
    const newWidth = node.width() * scaleX;
    setTextWidth(newWidth);
    node.setAttrs({
      width: newWidth,
      scaleX: 1,
    });
  }, []);

  return (
    <Stage width={window.innerWidth} height={window.innerHeight}>
      <Layer>
        <Text
          ref={textRef}
          text={text}
          x={50}
          y={80}
          fontSize={20}
          draggable
          width={textWidth}
          onDblClick={handleTextDblClick}
          onDblTap={handleTextDblClick}
          onTransform={handleTransform}
          visible={!isEditing}
        />
        {isEditing && (
          <TextEditor
            textNode={textRef.current}
            onChange={handleTextChange}
            onClose={() => setIsEditing(false)}
          />
        )}
        {!isEditing && (
          <Transformer
            ref={trRef}
            enabledAnchors={['middle-left', 'middle-right']}
            boundBoxFunc={(oldBox, newBox) => ({
              ...newBox,
              width: Math.max(30, newBox.width),
            })}
          />
        )}
      </Layer>
    </Stage>
  );
};

export default EditableText;

Open Sandbox

<template>
  <v-stage :config="stageSize">
    <v-layer>
      <v-text
        ref="textNode"
        :config="{
          text: text,
          x: 50,
          y: 80,
          fontSize: 20,
          draggable: true,
          width: textWidth,
          visible: !isEditing,
        }"
        @dblclick="handleTextDblClick"
        @dbltap="handleTextDblClick"
        @transform="handleTransform"
      />
      <v-transformer
        v-if="!isEditing"
        ref="transformerNode"
        :config="{
          enabledAnchors: ['middle-left', 'middle-right'],
          boundBoxFunc: (oldBox, newBox) => {
            newBox.width = Math.max(30, newBox.width);
            return newBox;
          },
        }"
      />
    </v-layer>
  </v-stage>
</template>

<script setup>
import { ref, onMounted } from 'vue';

Konva._fixTextRendering = true;

const stageSize = {
  width: window.innerWidth,
  height: window.innerHeight
};

const text = ref('一些文本');
const textWidth = ref(200);
const isEditing = ref(false);
const textNode = ref(null);
const transformerNode = ref(null);

onMounted(() => {
  transformerNode.value.getNode().nodes([textNode.value.getNode()]);
});

const handleTextDblClick = () => {
  const textNodeKonva = textNode.value.getNode();
  const stage = textNodeKonva.getStage();
  const textPosition = textNodeKonva.absolutePosition();
  const stageBox = stage.container().getBoundingClientRect();

  const areaPosition = {
    x: stageBox.left + textPosition.x,
    y: stageBox.top + textPosition.y,
  };

  const textarea = document.createElement('textarea');
  document.body.appendChild(textarea);

  textarea.value = textNodeKonva.text();
  textarea.style.position = 'absolute';
  textarea.style.top = areaPosition.y + 'px';
  textarea.style.left = areaPosition.x + 'px';
  textarea.style.width = textNodeKonva.width() - textNodeKonva.padding() * 2 + 'px';
  textarea.style.height = textNodeKonva.height() - textNodeKonva.padding() * 2 + 5 + 'px';
  textarea.style.fontSize = textNodeKonva.fontSize() + 'px';
  textarea.style.border = 'none';
  textarea.style.padding = '0px';
  textarea.style.margin = '0px';
  textarea.style.overflow = 'hidden';
  textarea.style.background = 'none';
  textarea.style.outline = 'none';
  textarea.style.resize = 'none';
  textarea.style.lineHeight = textNodeKonva.lineHeight();
  textarea.style.fontFamily = textNodeKonva.fontFamily();
  textarea.style.transformOrigin = 'left top';
  textarea.style.textAlign = textNodeKonva.align();
  textarea.style.color = textNodeKonva.fill();

  const rotation = textNodeKonva.rotation();
  let transform = '';
  if (rotation) {
    transform += 'rotateZ(' + rotation + 'deg)';
  }
  textarea.style.transform = transform;

  textarea.style.height = 'auto';
  textarea.style.height = textarea.scrollHeight + 3 + 'px';

  isEditing.value = true;
  textarea.focus();

  function removeTextarea() {
    textarea.parentNode.removeChild(textarea);
    window.removeEventListener('click', handleOutsideClick);
    isEditing.value = false;
  }

  function setTextareaWidth(newWidth) {
    if (!newWidth) {
      newWidth = textNodeKonva.placeholder?.length * textNodeKonva.fontSize();
    }
    textarea.style.width = newWidth + 'px';
  }

  textarea.addEventListener('keydown', function (e) {
    if (e.key === 'Enter' && !e.shiftKey) {
      text.value = textarea.value;
      removeTextarea();
    }
    if (e.key === 'Escape') {
      removeTextarea();
    }
  });

  textarea.addEventListener('keydown', function () {
    const scale = textNodeKonva.getAbsoluteScale().x;
    setTextareaWidth(textNodeKonva.width() * scale);
    textarea.style.height = 'auto';
    textarea.style.height = textarea.scrollHeight + textNodeKonva.fontSize() + 'px';
  });

  function handleOutsideClick(e) {
    if (e.target !== textarea) {
      text.value = textarea.value;
      removeTextarea();
    }
  }
  setTimeout(() => {
    window.addEventListener('click', handleOutsideClick);
    window.addEventListener('touchstart', handleOutsideClick);
  });
};

const handleTransform = (e) => {
  const node = textNode.value.getNode();
  textWidth.value = node.width() * node.scaleX();
  node.setAttrs({
    width: node.width() * node.scaleX(),
    scaleX: 1,
  });
};
</script>

Open Sandbox