ImageKnife组件，让小白也能轻松搞定图片开发 原创 精华

imageKnifeExecute() {
  // 首先需要确保获取ImageKnife单例对象
  if(ImageKnife){
  }else{
    ImageKnife = globalThis.exports.default.data.imageKnife;
  }
  // 生成配置信息requestOption
  let request = new RequestOption();
  // 配置必要信息和回调
  this.configNecessary(request);
  // 配置缓存相关信息   
  this.configCacheStrategy(request);
  // 配置显示信息和回调 
  this.configDisplay(request);
  // 启动ImageKnife执行请求
  ImageKnife.call(request);
}
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// 占位图解析成功
placeholderOnComplete(imageKnifeData: ImageKnifeData) {
// 主图未加载成功,并且未加载失败  显示占位图  主图加载成功或者加载失败后=>不展示占位图
  if (!this.loadMainReady && !this.loadErrorReady && !this.loadThumbnailReady) {
        this.placeholderFunc(imageKnifeData)
  }
}
// 加载失败 占位图解析成功
errorholderOnComplete(imageKnifeData: ImageKnifeData) {
  // 如果有错误占位图 先解析并保存在RequestOption中 等到加载失败时候进行调用
  this.errorholderData = imageKnifeData;
  if (this.loadErrorReady) {
    this.errorholderFunc(imageKnifeData)
  }
}
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// 移除较少使用的缓存数据
trimToSize(tempsize: number) {
  while (true) {
    if (tempsize < 0) {
      this.map.clear()
      this.size = 0
      break
    }
    if (this.size <= tempsize || this.map.isEmpty()) {
      break
    }
    var delkey = this.map.getFirstKey()
    this.map.remove(delkey)
    this.size--
  }
}
// 缓存数据最大值
maxSize(): number{
  return this.maxsize
}
// 设置缓存数据量最大值
resize(maxsize: number) {
  if (maxsize < 0) {
    throw new Error('maxsize <0 & maxsize invalid');
  }
  this.maxsize = maxsize
  this.trimToSize(maxsize)
}
// 清除缓存
evicAll() {
  this.trimToSize(-1)
}
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//读取journal文件的缓存数据
readJournal(path: string) {
  var fileReader = new FileReader(path)
  var line: string = ''
  while (!fileReader.isEnd()) {
    line = fileReader.readLine()
    line = line.replace('\n', '').replace('\r', '')
    this.dealwithJournal(line)
  }
  this.fileUtils.deleteFile(this.journalPathTemp)
  this.trimToSize()
}
//根据LRU算法删除多余缓存数据
private trimToSize() {
  while (this.size > this.maxSize) {
    var tempkey: string = this.cacheMap.getFirstKey()
    var fileSize = this.fileUtils.getFileSize(this.dirPath + tempkey)
    if (fileSize > 0) {
      this.size = this.size - fileSize
    }
    this.fileUtils.deleteFile(this.dirPath + tempkey)
    this.cacheMap.remove(tempkey)
    this.fileUtils.writeData(this.journalPath, 'remove ' + tempkey + '\n')
  }
}
//清除所有disk缓存数据
cleanCacheData() {
  var length = this.cacheMap.size()
  for (var index = 0; index < length; index++) {
    this.fileUtils.deleteFile(this.dirPath + this.cacheMap[index])
  }
  this.fileUtils.deleteFile(this.journalPath)
  this.cacheMap.clear()
  this.size = 0
}
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import image from '@ohos.multimedia.image'
export class TransformUtils {
  static centerCrop(buf: ArrayBuffer, outWidth: number, outHeihgt: number,
                    callback?: AsyncTransform<Promise<PixelMap>>) {
    // 创建媒体解码imageSource
    var imageSource = image.createImageSource(buf as any);
    // 获取图片信息
    imageSource.getImageInfo()
      .then((p) => {
        var sw;
        var sh;
        var scale;
        var pw = p.size.width;
        var ph = p.size.height;
        // 根据centerCrop规则控制缩放比例
        if (pw == outWidth && ph == outHeihgt) {
          sw = outWidth;
          sh = outHeihgt;
        } else {
          if (pw * outHeihgt > outWidth * ph) {
            scale = outHeihgt / ph;
          } else {
            scale = outWidth / pw;
          }
          sw = pw * scale;
          sh = ph * scale;
        }
        var options = {
          editable: true,
          rotate: 0,
          desiredRegion: { size: { width: sw, height: sh },
            x: pw / 2 - sw / 2,
            y: ph / 2 - sh / 2,
          },
        }
        if (callback) {
          // 回调，创建相关配置pixelmap
          callback('', imageSource.createPixelMap(options));
        }
      })
      .catch((error) => {
        callback(error, null);
      })
  }
}
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@Component
export struct ImageKnifeComponent {
  @Watch('watchImageKnifeOption') @Link imageKnifeOption: ImageKnifeOption;
  @State imageKnifePixelMapPack: PixelMapPack = new PixelMapPack();
  @State imageKnifeResource: Resource = $r('app.media.icon_loading')
  @State imageKnifeString: string = ''
  @State normalPixelMap: boolean = false;
  @State normalResource: boolean = true;
  previousData: ImageKnifeData = null;
  nowData: ImageKnifeData = null;
  build() {
    Stack() {
      //Image组件配置
      Image(this.normalPixelMap ? this.imageKnifePixelMapPack.pixelMap : (this.normalResource ? this.imageKnifeResource : this.imageKnifeString))
        .objectFit(this.imageKnifeOption.imageFit ? this.imageKnifeOption.imageFit : ImageFit.Fill)
        .visibility(this.imageVisible)
        .width(this.imageWidth)
        .height(this.imageHeight)
    }
  }
  //必要的用户配置和回调方法
  configNecessary(request: RequestOption){
    request.load(this.imageKnifeOption.loadSrc)
      .addListener((err, data) => {
        console.log('request.load callback')
        this.imageKnifeChangeSource(data)
        this.animateTo('image');
        return false;
      })
    if (this.imageKnifeOption.size) {
      request.setImageViewSize(this.imageKnifeOption.size)
    }
  }
  // imageknife 第一次启动和数据刷新后重新发送请求
  imageKnifeExecute() {
    let request = new RequestOption();
    this.configNecessary(request);
    this.configCacheStrategy(request);
    this.configDisplay(request);
    ImageKnife.call(request);
  }
  //返回数据Image渲染展示图片
  imageKnifeSpecialFixed(data:ImageKnifeData) {
    if (data.isPixelMap()) {
      this.displayPixelMap(data);
    }
    else if (data.isString()) {
      this.displayString(data);
    } else if (data.isResource()) {
      this.displayResource(data);
    } else {
    }
  }
}
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import {ImageKnife} from '@ohos/imageknife'
export default {
  data: {
    imageKnife: {} // ImageKnife
  },
  onCreate() {
    this.data.imageKnife = ImageKnife.with();
  },
  onDestroy() {
  },
}
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@Entry
@Component
struct Index {
  build() {
  }
  // 页面初始化完成，生命周期回调函数中 进行调用ImageKnife
  aboutToAppear() {
    let requestOption = new RequestOption();
  requestOptin.load($r('app.media.IceCream'))
  .addListener((err,data) => {
      //加载成功/失败回调监听
    })
    ...
  ImageKnife.call(requestOption)
  }
}
var ImageKnife;
var defaultTemp = globalThis.exports.default
if (defaultTemp != undefined) {
  ImageKnife = defaultTemp.data.imageKnife;
}
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import {ImageKnifeOption} from '@ohos/imageknife'
@Entry
@Component
struct Index {
  @State imageKnifeOption1: ImageKnifeOption =
    {
      loadSrc: $r('app.media.gifSample'),
      size: { width: 300, height: 300 },
      placeholderSrc: $r('app.media.icon_loading'),
      errorholderSrc: $r('app.media.icon_failed')
    };
  build() {
    Scroll() {
      Flex({ direction: FlexDirection.Column, alignItems: ItemAlign.Center, justifyContent: FlexAlign.Center }) {
        ImageKnifeComponent({ imageKnifeOption: $imageKnifeOption1 })
      }
    }
    .width('100%')
    .height('100%')
  }
}
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