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PowerImage

一个充分利用原生图片库能力、高扩展性的flutter图片库。

English document

特点：

  • 支持加载 ui.Image 能力。在基于外接纹理的方案中，使用方无法拿到真正的 ui.Image 去使用，这导致图片库在这种特殊的使用场景下无能为力。

  • 支持图片预加载能力。正如原生precacheImage一样。这在某些对图片展示速度要求较高的场景下非常有用。

  • 新增纹理缓存，与原生图片库缓存打通！统一图片缓存，避免原生图片混用带来的内存问题。

  • 支持模拟器。在 flutter-1.23.0-18.1.pre之前的版本，模拟器无法展示 Texture Widget。

  • 完善自定义图片类型通道。解决业务自定义图片获取诉求。

  • 完善的异常捕获与收集。

  • 支持动图。（来自淘特的 PR）

使用

安装

将下方配置加入到 pubspec.yaml 文件中:

dependencies:
  power_image: 0.1.0-pre.2
      
dependency_overrides:
  power_image_ext: 2.5.3

或者直接引用 GitHub 源码：

dependencies:
  power_image:
    git:
      url: 'git@github.com:alibaba/power_image.git'
      ref: '0.1.0-pre.2'

dependency_overrides:
  power_image_ext:
    git:
      url: 'git@github.com:alibaba/power_image_ext.git'
      ref: '2.5.3'

初始化

Flutter

1. 用 ImageCacheExt替换 ImageCache .

/// call before runApp()
PowerImageBinding();

or

/// return ImageCacheExt in createImageCache(), 
/// if you have extends with WidgetsFlutterBinding
class XXX extends WidgetsFlutterBinding {
  @override
  ImageCache createImageCache() {
    return ImageCacheExt();
  }
}

2. 初始化 PowerImageLoader

初始化并设置全局的默认的渲染方式，renderingTypeTexture为texture方式，renderingTypeExternal为ffi方式

另外PowerImageSetupOptions里面也有异常上报，以及异常上报采样率。

    PowerImageLoader.instance.setup(PowerImageSetupOptions(renderingTypeTexture,
        errorCallbackSamplingRate: 1.0,
        errorCallback: (PowerImageLoadException exception) {

    }));

iOS

PowerImage 提供了基础的图片类型，包括网络图（network）、文件（file）、native 资源（nativeAsset）、flutter 资源（asset），使用方需要自定义对应的加载器。

OC

    [[PowerImageLoader sharedInstance] registerImageLoader:[PowerImageNetworkImageLoader new] forType:kPowerImageImageTypeNetwork];
    [[PowerImageLoader sharedInstance] registerImageLoader:[PowerImageAssetsImageLoader new] forType:kPowerImageImageTypeNativeAsset];
    [[PowerImageLoader sharedInstance] registerImageLoader:[PowerImageFlutterAssertImageLoader new] forType:kPowerImageImageTypeAsset];
    [[PowerImageLoader sharedInstance] registerImageLoader:[PowerImageFileImageLoader new] forType:kPowerImageImageTypeFile];

Swift

        PowerImageLoader.sharedInstance().register(PowerImageNetworkImageLoader.init(), forType: kPowerImageImageTypeNetwork)
        PowerImageLoader.sharedInstance().register(PowerImageAssetsImageLoader.init(), forType: kPowerImageImageTypeNativeAsset)
        PowerImageLoader.sharedInstance().register(PowerImageFlutterAssertImageLoader.init(), forType: kPowerImageImageTypeAsset)
        PowerImageLoader.sharedInstance().register(PowerImageFileImageLoader.init(), forType: kPowerImageImageTypeFile)

loader 需要遵循 PowerImageLoaderProtocol 协议：

typedef void(^PowerImageLoaderCompletionBlock)(BOOL success, PowerImageResult *imageResult);

@protocol PowerImageLoaderProtocol <NSObject>
@required
- (void)handleRequest:(PowerImageRequestConfig *)requestConfig completed:(PowerImageLoaderCompletionBlock)completedBlock;
@end

Network image loader example:

OC

- (void)handleRequest:(PowerImageRequestConfig *)requestConfig completed:(PowerImageLoaderCompletionBlock)completedBlock {
    
    /// CDN optimization, you need transfer reqSize to native image loader!
    /// CDN optimization, you need transfer reqSize to native image loader!
    /// like this: [[SDWebImageManager sharedManager] downloadImageWithURL:[NSURL URLWithString:requestConfig.srcString] viewSize:reqSize completed:
    CGSize reqSize = requestConfig.originSize;
    /// attention.

    
    [[SDWebImageManager sharedManager] loadImageWithURL:[NSURL URLWithString:requestConfig.srcString] options:nil progress:^(NSInteger receivedSize, NSInteger expectedSize, NSURL * _Nullable targetURL) {

        } completed:^(UIImage * _Nullable image, NSData * _Nullable data, NSError * _Nullable error, SDImageCacheType cacheType, BOOL finished, NSURL * _Nullable imageURL) {
            if (image != nil) {
                completedBlock([PowerImageResult successWithImage:image]);
            }else {
                completedBlock([PowerImageResult failWithMessage:error.localizedDescription]);
            }
    }];

}

Swift

func handleRequest(_ requestConfig: PowerImageRequestConfig!, completed completedBlock: PowerImageLoaderCompletionBlock!) {
        let reqSize:CGSize = requestConfig.originSize
        let url = URL(string: requestConfig.srcString())
        SDWebImageManager.shared.loadImage(with: url, progress: nil) { image, data, error, cacheType, finished, url in
            
            if let image = image {
                if (image.sd_isAnimated) {
                    let frames:[SDImageFrame] = SDImageCoderHelper.frames(from: image)!
                    if frames.count > 0 {
                        var arr:[PowerImageFrame] = []
                        for index in 0..<frames.count {
                            let frame:SDImageFrame = frames[index]
                            arr.append(PowerImageFrame(image: frame.image, duration: frame.duration))
                        }
                        let flutterImage = PowerFlutterMultiFrameImage(image: image, frames: arr)
                        completedBlock(PowerImageResult.success(with: flutterImage))
                        return
                    }
                }
                
                completedBlock(PowerImageResult.success(with: image))
                
            }else{
                completedBlock(PowerImageResult.fail(withMessage: error?.localizedDescription ?? "PowerImageNetworkLoaderError!"))
            }   
       }
}

native asset loader example:

OC

- (void)handleRequest:(PowerImageRequestConfig *)requestConfig completed:(PowerImageLoaderCompletionBlock)completedBlock {
    UIImage *image = [UIImage imageNamed:requestConfig.srcString];
    if (image) {
        completedBlock([PowerImageResult successWithImage:image]);
    }else {
        completedBlock([PowerImageResult failWithMessage:@"MyAssetsImageLoader UIImage imageNamed: nil"]);
    }
}

Swift

func handleRequest(_ requestConfig: PowerImageRequestConfig!, completed completedBlock: PowerImageLoaderCompletionBlock!) {
        
        let image = UIImage(named: requestConfig.srcString())
        
        if let image = image {
            completedBlock(PowerImageResult.success(with: image))
        }else{
            completedBlock(PowerImageResult.fail(withMessage: "PowerImageAssetsImageLoaderError!"))
        }
    }

flutter asset loader example:

OC

- (void)handleRequest:(PowerImageRequestConfig *)requestConfig completed:(PowerImageLoaderCompletionBlock)completedBlock {
    UIImage *image = [self flutterImageWithName:requestConfig];
    if (image) {
        completedBlock([PowerImageResult successWithImage:image]);
    } else {
        completedBlock([PowerImageResult failWithMessage:@"flutterImageWithName nil"]);
    }
}

- (UIImage*)flutterImageWithName:(PowerImageRequestConfig *)requestConfig {
    NSString *name = requestConfig.srcString;
    NSString *package = requestConfig.src[@"package"];
    NSString *filename = [name lastPathComponent];
    NSString *path = [name stringByDeletingLastPathComponent];
    for (int screenScale = [UIScreen mainScreen].scale; screenScale > 1; --screenScale) {
        NSString *key = [self lookupKeyForAsset:[NSString stringWithFormat:@"%@/%d.0x/%@", path, screenScale, filename] fromPackage:package];
        UIImage *image = [UIImage imageNamed:key inBundle:[NSBundle mainBundle] compatibleWithTraitCollection:nil];
        if (image) {
            return image;
        }
    }
    NSString *key = [self lookupKeyForAsset:name fromPackage:package];

    /// webp iOS < 14 not support 
    if ([name hasSuffix:@".webp"] && !(@available(ios 14.0, *))) {
        NSString *mPath = [[NSBundle mainBundle] pathForResource:key ofType:nil];
        NSData *webpData = [NSData dataWithContentsOfFile:mPath];
        return [UIImage sd_imageWithWebPData:webpData];
    }
    return [UIImage imageNamed:key inBundle:[NSBundle mainBundle] compatibleWithTraitCollection:nil];
}

- (NSString *)lookupKeyForAsset:(NSString *)asset fromPackage:(NSString *)package {
    if (package && [package isKindOfClass:[NSString class]] && ![package isEqualToString:@""]) {
        return [FlutterDartProject lookupKeyForAsset:asset fromPackage:package];
    }else {
        return [FlutterDartProject lookupKeyForAsset:asset];
    }
}

Swift

func handleRequest(_ requestConfig: PowerImageRequestConfig!, completed completedBlock: PowerImageLoaderCompletionBlock!) {
        let image = self.flutterImage(requestConfig: requestConfig)
        if let image = image {
            completedBlock(PowerImageResult.success(with: image))
        }else {
            completedBlock(PowerImageResult.fail(withMessage: "PowerImageFlutterAssertImageLoaderError"))
        }
    }
    
    
    private func flutterImage(requestConfig:PowerImageRequestConfig) -> UIImage? {
        
        let name:String = requestConfig.srcString()!
        let package:String? = requestConfig.src["package"] as? String
        let fileName:String = NSString(string: name).lastPathComponent
        let path:String = NSString(string: name).deletingLastPathComponent
        
        
        let scaleArr:[Int] = (2...Int(UIScreen.main.scale)).reversed()
        
        for scale in scaleArr {
            let key:String = self.lookupKeyForAsset(asset: String(format: "%s/%d.0x/%s", path,scale,fileName), package: package)
            let image = UIImage(named: key,in: Bundle.main,compatibleWith: nil)
            if image != nil {
                return image!
            }
        }
        
        let key = self.lookupKeyForAsset(asset: name, package: package)
        return UIImage(named: key,in: Bundle.main,compatibleWith: nil)
    }
    
    private func lookupKeyForAsset(asset:String,package:String?) -> String {
        if let package = package, package != "" {
            return FlutterDartProject.lookupKey(forAsset: asset,fromPackage: package)
        }else{
            return FlutterDartProject.lookupKey(forAsset: asset)
        }
    }

file loader example:

OC

- (void)handleRequest:(PowerImageRequestConfig *)requestConfig completed:(PowerImageLoaderCompletionBlock)completedBlock {
    
    UIImage *image = [[UIImage alloc] initWithContentsOfFile:requestConfig.srcString];

    if (image) {
        completedBlock([PowerImageResult successWithImage:image]);
    } else {
        completedBlock([PowerImageResult failWithMessage:@"UIImage initWithContentsOfFile nil"]);
    }
}

Swift

func handleRequest(_ requestConfig: PowerImageRequestConfig!, completed completedBlock: PowerImageLoaderCompletionBlock!) {
        
        let image = UIImage(contentsOfFile: requestConfig.srcString())
        
        if let image = image {
            completedBlock(PowerImageResult.success(with: image))
        }else{
            completedBlock(PowerImageResult.fail(withMessage: "PowerImageFileImageLoaderError!"))
        }
    }

Android

PowerImage 提供了基础的图片类型，包括网络图（network）、文件（file）、native 资源（nativeAsset）、flutter 资源（asset），使用方需要自定义对应的加载器。

Java

PowerImageLoader.getInstance().registerImageLoader(
                new PowerImageNetworkLoader(this.getApplicationContext()), "network");
PowerImageLoader.getInstance().registerImageLoader(
                new PowerImageNativeAssetLoader(this.getApplicationContext()), "nativeAsset");
PowerImageLoader.getInstance().registerImageLoader(
                new PowerImageFlutterAssetLoader(this.getApplicationContext()), "asset");
PowerImageLoader.getInstance().registerImageLoader(
                new PowerImageFileLoader(this.getApplicationContext()), "file");

Kotlin

PowerImageLoader.getInstance().registerImageLoader(
            PowerImageNetworkLoader(this.applicationContext), "network"
)
PowerImageLoader.getInstance().registerImageLoader(
            PowerImageNativeAssetLoader(this.applicationContext), "nativeAsset"
)
PowerImageLoader.getInstance().registerImageLoader(
            PowerImageFlutterAssetLoader(this.applicationContext), "asset"
)
PowerImageLoader.getInstance().registerImageLoader(
            PowerImageFileLoader(this.applicationContext), "file"
)

loader 需要遵循 PowerImageLoaderProtocol 协议：

public interface PowerImageLoaderProtocol {
    void handleRequest(PowerImageRequestConfig request, PowerImageResult result);
}

Network image loader example:

Java

public class PowerImageNetworkLoader implements PowerImageLoaderProtocol {

    private Context context;

    public PowerImageNetworkLoader(Context context) {
        this.context = context;
    }

    @Override
    public void handleRequest(PowerImageRequestConfig request, PowerImageResponse response) {
        Glide.with(context).asDrawable().load(request.srcString()).listener(new RequestListener<Drawable>() {
            @Override
            public boolean onLoadFailed(@Nullable GlideException e, Object model, Target<Drawable> target, boolean isFirstResource) {
                response.onResult(PowerImageResult.genFailRet("Native加载失败: " + (e != null ? e.getMessage() : "null")));
                return true;
            }

            @Override
            public boolean onResourceReady(Drawable resource, Object model, Target<Drawable> target, DataSource dataSource, boolean isFirstResource) {
                if (resource instanceof GifDrawable) {
                    response.onResult(PowerImageResult.genSucRet(new GlideMultiFrameImage((GifDrawable) resource, false)));
                } else {
                    if (resource instanceof BitmapDrawable) {
                        response.onResult(PowerImageResult.genSucRet(new FlutterSingleFrameImage((BitmapDrawable) resource)));
                    } else {
                        response.onResult(PowerImageResult.genFailRet("Native加载失败:  resource : " + String.valueOf(resource)));
                    }
                }
                return true;
            }
        }).submit(request.width <= 0 ? Target.SIZE_ORIGINAL : request.width,
                request.height <= 0 ? Target.SIZE_ORIGINAL : request.height);
    }
}

Kotlin

class PowerImageNetworkLoader(private val context: Context) : PowerImageLoaderProtocol {
    override fun handleRequest(request: PowerImageRequestConfig, response: PowerImageResponse) {
        Glide.with(context).asDrawable().load(request.srcString())
            .listener(object : RequestListener<Drawable> {
                override fun onLoadFailed(
                    e: GlideException?,
                    model: Any,
                    target: Target<Drawable>,
                    isFirstResource: Boolean
                ): Boolean {
                    response.onResult(PowerImageResult.genFailRet("Native加载失败: " + if (e != null) e.message else "null"))
                    return true
                }

                override fun onResourceReady(
                    resource: Drawable,
                    model: Any,
                    target: Target<Drawable>,
                    dataSource: DataSource,
                    isFirstResource: Boolean
                ): Boolean {
                    if (resource is GifDrawable) {
                        response.onResult(
                            PowerImageResult.genSucRet(
                                GlideMultiFrameImage(
                                    resource as GifDrawable,
                                    false
                                )
                            )
                        )
                    } else {
                        if (resource is BitmapDrawable) {
                            response.onResult(
                                PowerImageResult.genSucRet(
                                    FlutterSingleFrameImage(
                                        resource as BitmapDrawable
                                    )
                                )
                            )
                        } else {
                            response.onResult(PowerImageResult.genFailRet("Native加载失败:  resource : $resource"))
                        }
                    }
                    return true
                }
            }).submit(
                if (request.width <= 0) Target.SIZE_ORIGINAL else request.width,
                if (request.height <= 0) Target.SIZE_ORIGINAL else request.height
            )
    }
}

native asset loader example:

Java

public class PowerImageNativeAssetLoader implements PowerImageLoaderProtocol {

    private Context context;

    public PowerImageNativeAssetLoader(Context context) {
        this.context = context;
    }

    @Override
    public void handleRequest(PowerImageRequestConfig request, PowerImageResponse response) {
        Resources resources = context.getResources();
        int resourceId = 0;
        try {
            resourceId = resources.getIdentifier(request.srcString(),
                    "drawable", context.getPackageName());
        } catch (Resources.NotFoundException e) {
            // 资源未找到
            e.printStackTrace();
        }
        if (resourceId == 0) {
            response.onResult(PowerImageResult.genFailRet("资源未找到"));
            return;
        }
        Glide.with(context).asBitmap().load(resourceId).listener(new RequestListener<Bitmap>() {
            @Override
            public boolean onLoadFailed(@Nullable GlideException e, Object model, Target<Bitmap> target, boolean isFirstResource) {
                response.onResult(PowerImageResult.genFailRet("Native加载失败: " + (e != null ? e.getMessage() : "null")));
                return true;
            }

            @Override
            public boolean onResourceReady(Bitmap resource, Object model, Target<Bitmap> target, DataSource dataSource, boolean isFirstResource) {
                response.onResult(PowerImageResult.genSucRet(resource));
                return true;
            }
        }).submit(request.width <= 0 ? Target.SIZE_ORIGINAL : request.width,
                request.height <= 0 ? Target.SIZE_ORIGINAL : request.height);
    }
}

Kotlin

class PowerImageNativeAssetLoader(private val context: Context) : PowerImageLoaderProtocol {
    override fun handleRequest(request: PowerImageRequestConfig, response: PowerImageResponse) {
        val resources = context.resources
        var resourceId = 0
        try {
            resourceId = resources.getIdentifier(
                request.srcString(),
                "drawable", context.packageName
            )
        } catch (e: Resources.NotFoundException) {
            // 资源未找到
            e.printStackTrace()
        }
        if (resourceId == 0) {
            response.onResult(PowerImageResult.genFailRet("资源未找到"))
            return
        }
        Glide.with(context).asBitmap().load(resourceId).listener(object : RequestListener<Bitmap?> {
            override fun onLoadFailed(
                e: GlideException?,
                model: Any,
                target: Target<Bitmap?>,
                isFirstResource: Boolean
            ): Boolean {
                response.onResult(PowerImageResult.genFailRet("Native加载失败: " + if (e != null) e.message else "null"))
                return true
            }

            override fun onResourceReady(
                resource: Bitmap?,
                model: Any,
                target: Target<Bitmap?>,
                dataSource: DataSource,
                isFirstResource: Boolean
            ): Boolean {
                response.onResult(PowerImageResult.genSucRet(resource))
                return true
            }
        }).submit(
            if (request.width <= 0) Target.SIZE_ORIGINAL else request.width,
            if (request.height <= 0) Target.SIZE_ORIGINAL else request.height
        )
    }
}

flutter asset loader example:

Java

public class PowerImageFlutterAssetLoader implements PowerImageLoaderProtocol {

    private Context context;

    public PowerImageFlutterAssetLoader(Context context) {
        this.context = context;
    }

    @Override
    public void handleRequest(PowerImageRequestConfig request, PowerImageResponse response) {
        String name = request.srcString();
        if (name == null || name.length() <= 0) {
            response.onResult(PowerImageResult.genFailRet("src 为空"));
            return;
        }
        String assetPackage = "";
        if (request.src != null) {
            assetPackage = (String) request.src.get("package");
        }
        String path;
        if (assetPackage != null && assetPackage.length() > 0) {
            path = FlutterMain.getLookupKeyForAsset(name, assetPackage);
        } else {
            path = FlutterMain.getLookupKeyForAsset(name);
        }
        if (path == null || path.length() <= 0) {
            response.onResult(PowerImageResult.genFailRet("path 为空"));
            return;
        }
        Uri asset = Uri.parse("file:///android_asset/" + path);
        Glide.with(context).asBitmap().load(asset).listener(new RequestListener<Bitmap>() {
            @Override
            public boolean onLoadFailed(@Nullable GlideException e, Object model, Target<Bitmap> target, boolean isFirstResource) {
                response.onResult(PowerImageResult.genFailRet("Native加载失败: " + (e != null ? e.getMessage() : "null")));
                return true;
            }

            @Override
            public boolean onResourceReady(Bitmap resource, Object model, Target<Bitmap> target, DataSource dataSource, boolean isFirstResource) {
                response.onResult(PowerImageResult.genSucRet(resource));
                return true;
            }
        }).submit(request.width <= 0 ? Target.SIZE_ORIGINAL : request.width,
                request.height <= 0 ? Target.SIZE_ORIGINAL : request.height);
    }

}

file loader example:

Java

public class PowerImageFileLoader implements PowerImageLoaderProtocol {

    private final Context context;

    public PowerImageFileLoader(Context context) {
        this.context = context;
    }

    @Override
    public void handleRequest(PowerImageRequestConfig request, PowerImageResponse response) {
        String name = request.srcString();
        if (name == null || name.length() <= 0) {
            response.onResult(PowerImageResult.genFailRet("src 为空"));
            return;
        }
        Uri asset = Uri.parse("file://" + name);
        Glide.with(context).asBitmap().load(asset).listener(new RequestListener<Bitmap>() {
            @Override
            public boolean onLoadFailed(@Nullable GlideException e, Object model, Target<Bitmap> target, boolean isFirstResource) {
                response.onResult(PowerImageResult.genFailRet("Native加载失败: " + (e != null ? e.getMessage() : "null")));
                return true;
            }

            @Override
            public boolean onResourceReady(Bitmap resource, Object model, Target<Bitmap> target, DataSource dataSource, boolean isFirstResource) {
                response.onResult(PowerImageResult.genSucRet(resource));
                return true;
            }
        }).submit(request.width <= 0 ? Target.SIZE_ORIGINAL : request.width,
                request.height <= 0 ? Target.SIZE_ORIGINAL : request.height);
    }
}

Kotlin

class PowerImageFileLoader(private val context: Context) : PowerImageLoaderProtocol {
    override fun handleRequest(request: PowerImageRequestConfig, response: PowerImageResponse) {
        val name = request.srcString()
        if (name == null || name.length <= 0) {
            response.onResult(PowerImageResult.genFailRet("src 为空"))
            return
        }
        val asset = Uri.parse("file://$name")
        Glide.with(context).asBitmap().load(asset).listener(object : RequestListener<Bitmap?> {
            override fun onLoadFailed(
                e: GlideException?,
                model: Any,
                target: Target<Bitmap?>,
                isFirstResource: Boolean
            ): Boolean {
                response.onResult(PowerImageResult.genFailRet("Native加载失败: " + if (e != null) e.message else "null"))
                return true
            }

            override fun onResourceReady(
                resource: Bitmap?,
                model: Any,
                target: Target<Bitmap?>,
                dataSource: DataSource,
                isFirstResource: Boolean
            ): Boolean {
                response.onResult(PowerImageResult.genSucRet(resource))
                return true
            }
        }).submit(
            if (request.width <= 0) Target.SIZE_ORIGINAL else request.width,
            if (request.height <= 0) Target.SIZE_ORIGINAL else request.height
        )
    }
}

API

network image:

  PowerImage.network(
    String src, {
    Key? key,
    String? renderingType,
    double? imageWidth,
    double? imageHeight,
    this.width,
    this.height,
    this.frameBuilder,
    this.errorBuilder,
    this.fit = BoxFit.cover,
    this.alignment = Alignment.center,
    this.semanticLabel,
    this.excludeFromSemantics = false,
  })

nativeAsset:

PowerImage.nativeAsset(
    String src, {
    Key? key,
    String? renderingType,
    double? imageWidth,
    double? imageHeight,
    this.width,
    this.height,
    this.frameBuilder,
    this.errorBuilder,
    this.fit = BoxFit.cover,
    this.alignment = Alignment.center,
    this.semanticLabel,
    this.excludeFromSemantics = false,
  })

Flutter asset:

  PowerImage.asset(
    String src, {
    Key? key,
    String? renderingType,
    double? imageWidth,
    double? imageHeight,
    String? package,
    this.width,
    this.height,
    this.frameBuilder,
    this.errorBuilder,
    this.fit = BoxFit.cover,
    this.alignment = Alignment.center,
    this.semanticLabel,
    this.excludeFromSemantics = false,
  })

File:

  PowerImage.file(String src,
      {Key key,
      this.width,
      this.height,
      this.frameBuilder,
      this.errorBuilder,
      this.fit = BoxFit.cover,
      this.alignment = Alignment.center,
      String renderingType,
      double imageWidth,
      double imageHeight})

自定义来源图片:

1.自定义 imageType，比如 “album”。

2.自定义 src（PowerImageRequestOptionsSrc），里面放需要传递给native的自定义参数。

3.Native侧自定义Loader，接收Flutter侧传递的参数，然后返回一个Bitmap或UIImage，并注册该Loader。

4.Flutter侧就可以展示自定义的图片了。

  /// 自定义 imageType\src
  /// 效果：将src encode 后，完成地传递给 native 对应 imageType 注册的 loader
  /// 使用场景：
  /// 例如，自定义加载相册照片，通过自定义 imageType 为 "album"，
  /// native 侧注册 "album" 类型的 loader 自定义图片的加载。  
PowerImage.type(
    String imageType, {
    required PowerImageRequestOptionsSrc src,
    Key? key,
    String? renderingType,
    double? imageWidth,
    double? imageHeight,
    this.width,
    this.height,
    this.frameBuilder,
    this.errorBuilder,
    this.fit = BoxFit.cover,
    this.alignment = Alignment.center,
    this.semanticLabel,
    this.excludeFromSemantics = false,
  })

.options

  /// 更加灵活的方式，通过自定义options来展示图片
  ///
  /// PowerImageRequestOptions({
  ///   @required this.src,   //资源
  ///   @required this.imageType, //资源类型，如网络图，本地图或者自定义等
  ///   this.renderingType, //渲染方式，默认全局
  ///   this.imageWidth,  //图片的渲染的宽度
  ///   this.imageHeight, //图片渲染的高度
  /// });
  ///
  /// PowerExternalImageProvider（FFI[bitmap]方案）
  /// PowerTextureImageProvider（texture方案）
  ///
  /// 使用场景：
  /// 例如，自定义加载相册照片，通过自定义 imageType 为 "album"，
  /// native 侧注册 "album" 类型的 loader 自定义图片的加载。
  ///
PowerImage.options(
    PowerImageRequestOptions options, {
    Key? key,
    this.width,
    this.height,
    this.frameBuilder,
    this.errorBuilder,
    this.fit = BoxFit.cover,
    this.alignment = Alignment.center,
    this.semanticLabel,
    this.excludeFromSemantics = false,
  })

Android

PowerImageLoader.getInstance().registerImageLoader(
  new PowerImageAlbumLoader(application.getApplicationContext()), "album");
public class PowerImageAlbumLoader implements PowerImageLoaderProtocol {

    private final Context context;

    public PowerImageAlbumLoader(Context context) {
        this.context = context;
    }

    @Override
    public void handleRequest(PowerImageRequestConfig request, final PowerImageResponse response) {
        Map<String, Object> src = request.src;
        if (src == null || src.get(Const.Argument.ASSET_ID) == null || src.get(Const.Argument.ASSET_TYPE) == null) {
            PowerImageResult result = PowerImageResult.genFailRet("asset id or assetType == null");
            response.onResult(result);
            return;
        }
        AssetQuality quality = AssetQuality.values()[(int) src.get(Const.Argument.QUALITY)];
        boolean highQuality = quality == AssetQuality.fullScreen;
        final LocalMedia media = new LocalMedia();
        media.fromMap(src);
        final ThumbnailLoader thumbnailLoader = new ThumbnailLoader(context);
        thumbnailLoader.load(media, highQuality, new ThumbnailLoader.ThumbnailLoadListener() {
            @Override
            public void onThumbnailLoaded(final Bitmap bitmap) {
                PowerImageResult result;
                if (bitmap == null) {
                    result = PowerImageResult.genFailRet("bitmap == null");
                } else {
                    result = PowerImageResult.genSucRet(bitmap);
                }
                response.onResult(result);
            }
        });
    }

}

iOS

[[PowerImageLoader sharedInstance] registerImageLoader:[AlbumAssetsImageLoader new] forType:@"album"];
- (void)handleRequest:(PowerImageRequestConfig *)requestConfig completed:(PowerImageLoaderCompletionBlock)completedBlock {
    NSString *assetId = requestConfig.src[@"assetId"];
    NSNumber *imageWidth = requestConfig.src[@"imageWidth"];
    NSNumber *imageHeight = requestConfig.src[@"imageHeight"];
    if (assetId) {
        if (imageWidth && imageHeight) {
            [[MPAssetManager sharedInstance] getImageWithAssetId:assetId
                                                       imageSize:CGSizeMake(imageWidth.doubleValue, imageHeight.doubleValue)
                                                  successHandler:^(UIImage *image) {
                completedBlock([PowerImageResult successWithImage:image]);
            } failureHandler:^(NSError *error) {
                completedBlock([PowerImageResult failWithMessage:error.localizedDescription]);
            }];
        } else {
            [[MPAssetManager sharedInstance] getThumbnail:assetId
                                           successHandler:^(UIImage *image) {
                completedBlock([PowerImageResult successWithImage:image]);
            } failureHandler:^(NSError *error) {
                completedBlock([PowerImageResult failWithMessage:error.localizedDescription]);
            }];
        }
    } else {
        completedBlock([PowerImageResult failWithMessage:@"assetId is nil"]);
    }
}

例子

Network

          return PowerImage.network(
            'https://flutter.github.io/assets-for-api-docs/assets/widgets/owl.jpg',
            width: 100,
            height: 100,
          );

最佳实践

最佳实践

原理

https://mp.weixin.qq.com/s/TdTGK21S-Yd3aD-yZDoYyQ