1.简介

Picasso是Square公司出品的一个强大的图片下载和缓存图片库
1）在adapter中需要取消已经不在视野范围的ImageView图片资源的加载，否则会导致图片错位，Picasso已经解决了这个问题。
2）使用复杂的图片压缩转换来尽可能的减少内存消耗
3）自带内存和硬盘二级缓存功能

2.基本用法

①普通加载图片

Picasso.with(PicassoActivity.this) 　　　　.load("http://n.sinaimg.cn/translate/20160819/9BpA-fxvcsrn8627957.jpg") 　　　　.into(ivPicassoResult1);

②裁剪的方式加载图片

Picasso.with(PicassoActivity.this) 　　　　.load("http://n.sinaimg.cn/translate/20160819/9BpA-fxvcsrn8627957.jpg")
　　　　.resize(100,100) 　　　　.into(ivPicassoResult1);

③选择180度

Picasso.with(PicassoActivity.this) 　　　　.load("http://n.sinaimg.cn/translate/20160819/9BpA-fxvcsrn8627957.jpg")
　　　　.rotate(180) 　　　　.into(ivPicassoResult1);

3.ListView资源加载的方法

- placeholder(xxx). 设置资源加载过程中的显示的Drawable。
- error(xxx).设置load失败时显示的Drawable。
- into(xxx) 设置资源加载到的目标 包括ImageView Target等

eg:Adapter中getView()方法中

// 加载图片 Picasso.with(mContext) .load(Constants.IMAGES[position]) .placeholder(R.drawable.atguigu_logo) .error(R.drawable.atguigu_logo) .into(holder.iv);

4.常用工具类

PicassoUtil { setImg(Context context, int resId, ImageView imgView){ 4 Picasso.with(context) 5 .load(resId) .fit() 8 .into(imgView); 9 } setImg(Context context,int resId,ImageView imgView,int weight,int height){ 12 Picasso.with(context) .config(Bitmap.Config.RGB_565).resize(weight,height).into(imgView); } setImg(Context context, String imgurl, int resId, ImageView imgView){ 20 Picasso.with(context) .config(Bitmap.Config.RGB_565).placeholder(resId).error(resId).fit().into(imgView); } setImg(Context context, String imgurl, ImageView imgView){ 29 Picasso.with(context) .config(Bitmap.Config.RGB_565).fit().into(imgView); } setImg(Context context, String imgurl, ViewPager imgView){ 37 Picasso.with(context) .config(Bitmap.Config.RGB_565).fit().into((Target) imgView); } setImg(Context context, String imgurl, int resId, ViewPager imgView){ 45 Picasso.with(context) .config(Bitmap.Config.RGB_565).placeholder(resId).error(resId).fit().into((Target) imgView); } setImg(Context context, String imgurl,ImageView imgView,int weight,int height){ 55 Picasso.with(context) .config(Bitmap.Config.RGB_565).resize(weight,height).into(imgView); } setImg(Context context, String imgurl, int resId,int weight,int height, ImageView imgView){ 63 Picasso.with(context) .config(Bitmap.Config.RGB_565).placeholder(resId).error(resId).resize(weight,height).into(imgView); } 71 }

5.图片变换

在module的gradle中添加转换库:

dependencies { compile 'jp.wasabeef:picasso-transformations:2.1.0' // If you want to use the GPU Filters compile 'jp.co.cyberagent.android.gpuimage:gpuimage-library:1.4.1' } repositories { jcenter() }

Activity中:

List<String> data = new ArrayList<>(); for (int i = 1; i<= 36; i++){ data.add(i+""); } // 初始化listview PicassoTransformationsAdapter picassoTransformationsAdapter = new PicassoTransformationsAdapter(PicassoTransfromationsActivity.this,data); lvPicassoTransfromations.setAdapter(picassoTransformationsAdapter);

PicassoListviewAdapter：

public class PicassoTransformationsAdapter extends BaseAdapter { private Context mContext; private List<String> mData; public PicassoTransformationsAdapter(Context context, List<String> data) { mContext = context; mData = data; } @Override public int getCount() { return mData == null ? 0 : mData.size(); } @Override public Object getItem(int position) { return null; } @Override public long getItemId(int position) { return 0; } @Override public View getView(int position, View convertView, ViewGroup parent) { ViewHolder holder; if(convertView == null) { convertView = View.inflate(mContext, R.layout.item_picasso_transformations,null); holder = new ViewHolder(convertView); convertView.setTag(holder); }else { holder = (ViewHolder) convertView.getTag(); } // 显示名称 holder.name.setText("item"+(position + 1)); int integer = Integer.parseInt(mData.get(position)); switch (integer) { case 1: { int width = Utils.dip2px(mContext, 133.33f); int height = Utils.dip2px(mContext, 126.33f); Picasso.with(mContext) .load(R.drawable.check) .resize(width, height) .centerCrop() .transform((new MaskTransformation(mContext, R.drawable.mask_starfish))) .into(holder.image); break; } case 2: { int width = Utils.dip2px(mContext, 150.0f); int height = Utils.dip2px(mContext, 100.0f); Picasso.with(mContext) .load(R.drawable.check) .resize(width, height) .centerCrop() .transform(new MaskTransformation(mContext, R.drawable.chat_me_mask)) .into(holder.image); break; } case 3: Picasso.with(mContext) .load(R.drawable.demo) .transform(new CropTransformation(300, 100, CropTransformation.GravityHorizontal.LEFT, CropTransformation.GravityVertical.TOP)) .into(holder.image); break; case 4: Picasso.with(mContext).load(R.drawable.demo) // 300, 100, CropTransformation.GravityHorizontal.LEFT, CropTransformation.GravityVertical.CENTER)) .transform(new CropTransformation(300, 100)).into(holder.image); break; case 5: Picasso.with(mContext) .load(R.drawable.demo) .transform(new CropTransformation(300, 100, CropTransformation.GravityHorizontal.LEFT, CropTransformation.GravityVertical.BOTTOM)) .into(holder.image); break; case 6: Picasso.with(mContext) .load(R.drawable.demo) .transform(new CropTransformation(300, 100, CropTransformation.GravityHorizontal.CENTER, CropTransformation.GravityVertical.TOP)) .into(holder.image); break; case 7: Picasso.with(mContext) .load(R.drawable.demo) .transform(new CropTransformation(300, 100)) .into(holder.image); break; case 8: Picasso.with(mContext) .load(R.drawable.demo) .transform(new CropTransformation(300, 100, CropTransformation.GravityHorizontal.CENTER, CropTransformation.GravityVertical.BOTTOM)) .into(holder.image); break; case 9: Picasso.with(mContext) .load(R.drawable.demo) .transform(new CropTransformation(300, 100, CropTransformation.GravityHorizontal.RIGHT, CropTransformation.GravityVertical.TOP)) .into(holder.image); break; case 10: Picasso.with(mContext) .load(R.drawable.demo) .transform(new CropTransformation(300, 100, CropTransformation.GravityHorizontal.RIGHT, CropTransformation.GravityVertical.CENTER)) .into(holder.image); break; case 11: Picasso.with(mContext) .load(R.drawable.demo) .transform(new CropTransformation(300, 100, CropTransformation.GravityHorizontal.RIGHT, CropTransformation.GravityVertical.BOTTOM)) .into(holder.image); break; case 12: Picasso.with(mContext) .load(R.drawable.demo) .transform(new CropTransformation((float) 16 / (float) 9, CropTransformation.GravityHorizontal.CENTER, CropTransformation.GravityVertical.CENTER)) .into(holder.image); break; case 13: Picasso.with(mContext) .load(R.drawable.demo) .transform(new CropTransformation((float) 4 / (float) 3, CropTransformation.GravityHorizontal.CENTER, CropTransformation.GravityVertical.CENTER)) .into(holder.image); break; case 14: Picasso.with(mContext) .load(R.drawable.demo) .transform(new CropTransformation(3, CropTransformation.GravityHorizontal.CENTER, CropTransformation.GravityVertical.CENTER)) .into(holder.image); break; case 15: Picasso.with(mContext) .load(R.drawable.demo) .transform(new CropTransformation(3, CropTransformation.GravityHorizontal.CENTER, CropTransformation.GravityVertical.TOP)) .into(holder.image); break; case 16: Picasso.with(mContext) .load(R.drawable.demo) .transform(new CropTransformation(1, CropTransformation.GravityHorizontal.CENTER, CropTransformation.GravityVertical.CENTER)) .into(holder.image); break; case 17: Picasso.with(mContext) .load(R.drawable.demo) .transform(new CropTransformation((float) 0.5, (float) 0.5, CropTransformation.GravityHorizontal.CENTER, CropTransformation.GravityVertical.CENTER)) .into(holder.image); break; case 18: Picasso.with(mContext) .load(R.drawable.demo) .transform(new CropTransformation((float) 0.5, (float) 0.5, CropTransformation.GravityHorizontal.CENTER, CropTransformation.GravityVertical.TOP)) .into(holder.image); break; case 19: Picasso.with(mContext) .load(R.drawable.demo) .transform(new CropTransformation((float) 0.5, (float) 0.5, CropTransformation.GravityHorizontal.RIGHT, CropTransformation.GravityVertical.BOTTOM)) .into(holder.image); break; case 20: Picasso.with(mContext) .load(R.drawable.demo) .transform(new CropTransformation((float) 0.5, 0, (float) 4 / (float) 3, CropTransformation.GravityHorizontal.CENTER, CropTransformation.GravityVertical.CENTER)) .into(holder.image); break; case 21: Picasso.with(mContext) .load(R.drawable.demo) .transform(new CropSquareTransformation()) .into(holder.image); break; case 22: Picasso.with(mContext) .load(R.drawable.demo) .transform(new CropCircleTransformation()) .into(holder.image); break; case 23: Picasso.with(mContext) .load(R.drawable.demo) .transform(new ColorFilterTransformation(Color.argb(80, 255, 0, 0))) .into(holder.image); break; case 24: Picasso.with(mContext) .load(R.drawable.demo) .transform(new GrayscaleTransformation()) .into(holder.image); break; case 25: Picasso.with(mContext) .load(R.drawable.demo) .transform(new RoundedCornersTransformation(30, 0, RoundedCornersTransformation.CornerType.BOTTOM_LEFT)) .into(holder.image); break; case 26: Picasso.with(mContext) .load(R.drawable.check) .transform(new BlurTransformation(mContext, 25, 1)) .into(holder.image); break; case 27: Picasso.with(mContext) .load(R.drawable.demo) .transform(new ToonFilterTransformation(mContext)) .into(holder.image); break; case 28: Picasso.with(mContext) .load(R.drawable.check) .transform(new SepiaFilterTransformation(mContext)) .into(holder.image); break; case 29: Picasso.with(mContext) .load(R.drawable.check) .transform(new ContrastFilterTransformation(mContext, 2.0f)) .into(holder.image); break; case 30: Picasso.with(mContext) .load(R.drawable.check) .transform(new InvertFilterTransformation(mContext)) .into(holder.image); break; case 31: Picasso.with(mContext) .load(R.drawable.check) .transform(new PixelationFilterTransformation(mContext, 20)) .into(holder.image); break; case 32: Picasso.with(mContext) .load(R.drawable.check) .transform(new SketchFilterTransformation(mContext)) .into(holder.image); break; case 33: Picasso.with(mContext) .load(R.drawable.check) .transform(new SwirlFilterTransformation(mContext, 0.5f, 1.0f, new PointF(0.5f, 0.5f))) .into(holder.image); break; case 34: Picasso.with(mContext) .load(R.drawable.check) .transform(new BrightnessFilterTransformation(mContext, 0.5f)) .into(holder.image); break; case 35: Picasso.with(mContext) .load(R.drawable.check) .transform(new KuwaharaFilterTransformation(mContext, 25)) .into(holder.image); break; case 36: Picasso.with(mContext) .load(R.drawable.check) .transform(new VignetteFilterTransformation(mContext, new PointF(0.5f, 0.5f), new float[]{0.0f, 0.0f, 0.0f}, 0f, 0.75f)) .into(holder.image); break; } return convertView; } class ViewHolder{ @Bind(R.id.iv_picasso) ImageView image; @Bind(R.id.tv_picasso) TextView name; public ViewHolder(View view) { ButterKnife.bind(this, view); } } }