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With the development of mobile Internet, more and more applications need to implement screenshot functions to improve user experience. During the development process, uniapp is a very popular cross-platform development framework. It provides a wealth of functions and interfaces that can be used to implement various functions, including screen capture. This article will introduce how uniapp implements the screen capture function.
1. The basic principle of screen capture in uniapp
In uniapp, the principle of screen capture is basically to use the interface wx.canvasToTempFilePath provided by the WeChat applet to capture part or all of the screen Next generate the temporary file path. Then, display the operation menu or preview image through the interface showActionSheet or showModal that comes with uniapp. The following is the code for a simple screen capture example:
export default { data() { return { canvasWidth: 0, canvasHeight: 0, canvasTop: 0, canvasLeft: 0 } }, methods: { getCanvas() { const query = uni.createSelectorQuery().in(this) query.select('#canvas-container').boundingClientRect(data => { uni.canvasToTempFilePath({ x: data.left, y: data.top, width: data.width, height: data.height, destWidth: data.width * 2, destHeight: data.height * 2, canvasId: 'canvas', success: res => { uni.showActionSheet({ itemList: ['预览图片', '保存图片'], success: res => { if (res.tapIndex == 0) { uni.previewImage({ urls: [res.tempFilePath] }) } else if (res.tapIndex == 1) { uni.saveImageToPhotosAlbum({ filePath: res.tempFilePath, success: () => { uni.showToast({ title: '保存成功!' }) }, fail: () => { uni.showToast({ title: '保存失败!' }) } }) } } }) }, fail: res => { uni.showToast({ title: '生成临时文件路径失败!' }) } }, this) }).exec() } } }
Among them, first obtain the width and height of the current page node through uni.createSelectorQuery().in(this), and then call the uni.canvasToTempFilePath interface to intercept the Some are saved as temporary files. In the success callback function of the interface, use uni.showActionSheet to display the operation menu. The user can choose to preview the picture or save the picture to the local album.
It should be noted that to implement the screen capture function, you need to define a canvas element in the current page to draw the content to be captured. The width, height and position of the canvas element need to be dynamically calculated to adapt to different screen sizes and positions.
2. Implementation steps of uniapp screen capture
The following will introduce the steps of uniapp to implement screen capture:
<canvas id="canvas" style="position: absolute; top: {{canvasTop}}px; left: {{canvasLeft}}px; width: {{canvasWidth}}px; height: {{canvasHeight}}px;"></canvas>
onReady() { setTimeout(() => { this.getCanvas() }, 500) },
const query = uni.createSelectorQuery().in(this) query.select('#canvas-container').boundingClientRect(data => { uni.canvasToTempFilePath({ x: data.left, y: data.top, width: data.width, height: data.height, destWidth: data.width * 2, destHeight: data.height * 2, canvasId: 'canvas', success: res => { // ... }, fail: res => { uni.showToast({ title: '生成临时文件路径失败!' }) } }, this) }).exec()
uni.showActionSheet({ itemList: ['预览图片', '保存图片'], success: res => { if (res.tapIndex == 0) { uni.previewImage({ urls: [res.tempFilePath] }) } else if (res.tapIndex == 1) { uni.saveImageToPhotosAlbum({ filePath: res.tempFilePath, success: () => { uni.showToast({ title: '保存成功!' }) }, fail: () => { uni.showToast({ title: '保存失败!' }) } }) } } })
3. Precautions for uniapp screen capture
In the process of implementing screen capture, you need to pay attention to the following matters:
4. Conclusion
Through the introduction of this article, we can see the basic principles and steps of uniapp to implement screen capture, and learn what needs to be paid attention to. By rationally applying the interfaces and functions provided by uniapp, the functional requirements of various applications can be quickly realized, the user experience can be improved, and a good user experience can be brought to users.
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