图片加载框架之Picasso

一、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

二、下载地址

点击下载链接

三、功能

1）基本用法

Picasso.with(context).load(imageUrl).into(imageView);

2）图片路径load()

    load SD卡资源：load("file://"+ Environment.getExternalStorageDirectory().getPath()+"/test.jpg")

    load assets资源：load("file:///android_asset/f003.gif")

   load drawable资源：load("android.resource://com.frank.glide/drawable/news")

  load http资源：load("http:www.123.com/1234567890.jpg")

3）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

4）图片裁剪

Picasso.with(this).load("http://n.sinaimg.cn/translate/20160819/9BpA-fxvcsrn8627957.jpg")  
                .resizeDimen(R.dimen.iv_width,R.dimen.iv_height)  

                .into(iv);

四、使用步骤

（1）导入jar包或在module的gradle文件中添加

 compile 'com.squareup.picasso:picasso:2.5.2'

五、例子

1）基本用法

普通加载

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

裁剪

        // 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(ivPicassoResult2);

旋转180度

        // 选择180度
        Picasso.with(PicassoActivity.this)
                .load("http://n.sinaimg.cn/translate/20160819/9BpA-fxvcsrn8627957.jpg")
                .rotate(180)
                .into(ivPicassoResult3);

2）listview中使用

        // 初始化listview
        PicassoListviewAdapter picassoListviewAdapter = new PicassoListviewAdapter(this);

        lvPicasso.setAdapter(picassoListviewAdapter);

public class PicassoListviewAdapter extends BaseAdapter {

    private Context mContext;

    public PicassoListviewAdapter(Context context) {
        mContext = context;
    }

    @Override
    public int getCount() {
        return Constants.IMAGES.length;
    }

    @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_listview,null);

            holder = new ViewHolder(convertView);

            convertView.setTag(holder);
        }else {
            holder = (ViewHolder) convertView.getTag();
        }

        // 名称
        holder.name.setText("item"+(position+1));

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

        return convertView;
    }

    class ViewHolder{
        @Bind(R.id.iv_picasso_item)
        ImageView iv;

        @Bind(R.id.tv_picasso_name)
        TextView name;

        public ViewHolder(View view) {
            ButterKnife.bind(this,view);
        }
    }
}

 3）转换案例

 private void initData() {
        // 标题
        tvTitle.setText("Picasso的转换操作");

        List 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);
    }

public class PicassoTransformationsAdapter extends BaseAdapter {
    private Context mContext;
    private List mData;

    public PicassoTransformationsAdapter(Context context, List 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);
        }
    }
}

工具类

public class Utils {
    public static int dip2px(Context context, float dp) {
        float scale = context.getResources().getDisplayMetrics().density;
        return (int) (dp * scale + 0.5f);
    }
}

提供一个工具类

public class PicassoUtil {
    //加载本地图片
    public static void setImg(Context context, int resId, ImageView imgView){
        Picasso.with(context)
                .load(resId)
                .config(Bitmap.Config.RGB_565)//8位RGB位图
                .fit()
                .into(imgView);
    }
    //按照一定的宽高加载本地图片，带有加载错误和默认图片
    public static void setImg(Context context,int resId,ImageView imgView,int weight,int height){
        Picasso.with(context)
                .load(resId)//加载本地图片
                .config(Bitmap.Config.RGB_565)//8位RGB位图
                .resize(weight,height)//设置图片的宽高
                .into(imgView);//把图片加载到控件上
    }
    //加载网络图片到imgview,带有加载错误和默认图片
    public static void setImg(Context context, String imgurl, int resId, ImageView imgView){
        Picasso.with(context)
                .load(imgurl)//加载网络图片的url
                .config(Bitmap.Config.RGB_565)//8位RGB位图
                .placeholder(resId)//默认图片
                .error(resId)//加载错误的图片
                .fit()//图片的宽高等于控件的宽高
                .into(imgView);//把图片加载到控件上
    }
    public static void setImg(Context context, String imgurl, ImageView imgView){
        Picasso.with(context)
                .load(imgurl)//加载网络图片的url
                .config(Bitmap.Config.RGB_565)//8位RGB位图
                .fit()//图片的宽高等于控件的宽高
                .into(imgView);//把图片加载到控件上
    }
    //加载网络图片到Viewpager
    public static void setImg(Context context, String imgurl, ViewPager imgView){
        Picasso.with(context)
                .load(imgurl)//加载网络图片的url
                .config(Bitmap.Config.RGB_565)//8位RGB位图
                .fit()//图片的宽高等于控件的宽高
                .into((Target) imgView);//把图片加载到控件上
    }
    //加载网络图片到Viewpager，带有加载错误和默认图片
    public static void setImg(Context context, String imgurl, int resId, ViewPager imgView){
        Picasso.with(context)
                .load(imgurl)//加载网络图片的url
                .config(Bitmap.Config.RGB_565)//8位RGB位图
                .placeholder(resId)//默认图片
                .error(resId)//加载错误的图片
                .fit()//图片的宽高等于控件的宽高
                .into((Target) imgView);//把图片加载到控件上
    }
    //按照设定的宽高加载网络图片到imgview
    public static void setImg(Context context, String imgurl,ImageView imgView,int weight,int height){
        Picasso.with(context)
                .load(imgurl)//加载网络图片的url
                .config(Bitmap.Config.RGB_565)//8位RGB位图
                .resize(weight,height)//设置图片的宽高
                .into(imgView);//把图片加载到控件上
    }
    //按照设定的宽高加载网络图片到imgview，带有加载错误和默认图片
    public static void setImg(Context context, String imgurl, int resId,int weight,int height, ImageView imgView){
        Picasso.with(context)
                .load(imgurl)//加载网络图片的url
                .config(Bitmap.Config.RGB_565)//8位RGB位图
                .placeholder(resId)//默认图片
                .error(resId)//加载错误的图片
                .resize(weight,height)//设置图片的宽高
                .into(imgView);//把图片加载到控件上
    }
}