前言

主要是参考了这篇文章链接，增加了一个builder构造器形式的构建参数以及对应的策略模式

1.先来讲讲策略模式

Paste_Image.png

这是策略模式的结构图，主要是定义一个任务，往往可以有多种不同的方式，每一种方式称为一个策略，我们可以根据环境或者条件的不同选择不同的策略来完成该项任务。
就拿这个图片加载来讲，加载图片是一个任务，你可以使用Glide,Fresco,Imageloader等策略来加载，一般而言任务都是抽象的，我使用接口来定义

public interface BaseImageLoaderStrategy<T extends ImageConfig> {  
    
  void loadImage(Context ctx, T config);  
    
}  

而且还对数据进行了封装，数据必须继承ImageConfig

public class ImageConfig {  
  protected String url;  
  protected int placeholder;  
  protected int errorPic;  
  
  public String getUrl() {  
    return url;  
  }  
  
  public int getPlaceholder() {  
    return placeholder;  
  }  
  
  public int getErrorPic() {  
    return errorPic;  
  }  
}  

里面要有url,用于请求资源的，然后用一个统一的类ImageLoader来管理这个

public class ImageLoader {  
  private static final ImageLoader INSTANCE = new ImageLoader();  
  private ImageLoader(){  
    //默认使用Glide  
    mStrategy=new GlideImageLoaderStrategy();  
  }  
  public static ImageLoader getInstance(){  
    return INSTANCE;  
  }  
  
  private BaseImageLoaderStrategy mStrategy;  
  
  public ImageLoader(BaseImageLoaderStrategy strategy) {  
    setLoadImgStrategy(strategy);  
  }  
  
  
  public <T extends ImageConfig> void loadImage(Context context, T config) {  
    this.mStrategy.loadImage(context, config);  
  }  
  
  
  public void setLoadImgStrategy(BaseImageLoaderStrategy strategy) {  
    this.mStrategy = strategy;  
  }  
  
}  

策略模式必须要指定使用哪种类型的策略，为了性能考虑，我把ImageLoader设置为单例

2.Glide的封装

public class GlideImageConfig extends ImageConfig {  
  
  private ImageView iamgeView;  
  
  private GlideImageConfig(Builder builder) {  
    url = builder.url;  
    placeholder = builder.placeholder;  
    errorPic = builder.errorPic;  
    iamgeView = builder.iamgeView;  
  }  
  
  public static Builder builder(){  
  
    return new Builder();  
  }  
  
  public ImageView getIamgeView() {  
    return iamgeView;  
  }  
  
  public static final class Builder {  
  
    private String url;  
    private ImageView imageView;  
    private int placeholder;  
    private int errorPic;  
    private ImageView iamgeView;  
  
    public Builder() {  
    }  
  
  
    public Builder url(String val) {  
      url = val;  
      return this;  
    }  
  
    public Builder placeholder(int val) {  
      placeholder = val;  
      return this;  
    }  
  
    public Builder errorPic(int val) {  
      errorPic = val;  
      return this;  
    }  
  
    public Builder iamgeView(ImageView val) {  
      iamgeView = val;  
      return this;  
    }  
  
    public GlideImageConfig build() {  
      return new GlideImageConfig(this);  
    }  
  }  
  
}  

数据使用Builder来封装，以后可以很容易扩展

public class GlideImageLoaderStrategy implements BaseImageLoaderStrategy<GlideImageConfig> {  
  
  @Override  
  public void loadImage(Context ctx, GlideImageConfig config) {  
  
    if (ctx == null) throw new IllegalStateException("Context is required");  
    if (config == null) throw new IllegalStateException("GlideImageConfig is required");  
    if (TextUtils.isEmpty(config.getUrl())) throw new IllegalStateException("url is required");  
    if (config.getIamgeView() == null) throw new IllegalStateException("imageview is required");  
    Glide.with(ctx).load(config.getUrl()).into(config.getIamgeView());  
  }  
}  

只需要继承BaseImageLoaderStrategy即可,以后也可以自己增加方法，参数都可以

3.对于Fresco的封装点不同，由于Fresco使用自建的SimpleDraweeView,它的数据封装有点不同

public class FrescoImageConfig extends ImageConfig {  
  
  private SimpleDraweeView imageView;  
  
  private FrescoImageConfig(Builder builder){  
    this.imageView = builder.imageView;  
    this.url = builder.url;  
    this.placeholder = builder.placeholder;  
    this.errorPic = builder.errorPic;  
  
  }  
  
  
  public static Builder builder(){  
    return new Builder();  
  }  
  
  public SimpleDraweeView getImageView() {  
    return imageView;  
  }  
  
  public static final class Builder{  
    private String url;  
    private SimpleDraweeView imageView;  
    private int placeholder;  
    private int errorPic;  
  
    private Builder(){  
  
    }  
    public Builder url(String url) {  
      this.url = url;  
      return this;  
    }  
  
    public Builder placeholder(int placeholder) {  
      this.placeholder = placeholder;  
      return this;  
    }  
  
    public Builder errorPic(int errorPic) {  
      this.errorPic = errorPic;  
      return this;  
    }  
  
    public Builder SimpleDraweeView(SimpleDraweeView imageView) {  
      this.imageView = imageView;  
      return this;  
    }  
    public FrescoImageConfig build(){  
      return new FrescoImageConfig(this);  
    }  
  }  
}  

而相应的策略类都是大同小异了

public class FrescoImageLoaderStrategy implements BaseImageLoaderStrategy<FrescoImageConfig> {  
  
  @Override  
  public void loadImage(Context ctx, FrescoImageConfig config) {  
    config.getImageView().setImageURI(Uri.parse(config.getUrl()));  
  }  
}  

详细代码请看demo 希望给个star