动态切换不同的图片加载框架

前言

 主要是参考了这篇文章点击打开链接，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

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);
}
}

}

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());
}
}

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()));
}
}