Picasso第三方图片框架显示图片

1:资源:

https://github.com/square/picasso](https://github.com/square/picasso

2:添加权限:

<uses-permission android:name="android.permission.INTERNET"/>

3.布局:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context="www.itcast.com.testpicasso.MainActivity">

    <Button
        android:id="@+id/btn"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Picasso" />

    <ImageView
        android:id="@+id/iv"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />
</LinearLayout>

　　4:显示普通图片

//显示普通图片
                Picasso
                        .with(this)// 指定Context
                        .load(url) //指定图片URL
                        .placeholder(R.mipmap.ic_launcher) //指定图片未加载成功前显示的图片
                        .error(R.mipmap.ic_launcher)// 指定图片加载失败显示的图片
                        .resize(400, 600)// 指定图片的尺寸
                        //.fit()// 指定图片缩放类型为fit
                        //.centerInside()// 指定图片缩放类型为centerInside
                       // .centerCrop()// 指定图片缩放类型为centerCrop
                        .memoryPolicy(MemoryPolicy.NO_CACHE, MemoryPolicy.NO_STORE)// 指定内存缓存策略
                        .priority(Picasso.Priority.HIGH)// 指定优先级
                        .into(iv1); // 指定显示图片的ImageView

　　5:显示圆形图片

  //显示圆形图片
                Transformation transform = new Transformation() {
                    @Override
                    public Bitmap transform(Bitmap source) {
                        int size = Math.min(source.getWidth(), source.getHeight());
                        int x = (source.getWidth() - size) / 2;
                        int y = (source.getHeight() - size) / 2;
                        Bitmap squaredBitmap = Bitmap.createBitmap(source, x, y, size, size);
                        if (squaredBitmap != source) {
                            source.recycle();
                        }
                        Bitmap bitmap = Bitmap.createBitmap(size, size, source.getConfig());
                        Canvas canvas = new Canvas(bitmap);
                        Paint paint = new Paint();
                        BitmapShader shader = new BitmapShader(squaredBitmap,
                                BitmapShader.TileMode.CLAMP, BitmapShader.TileMode.CLAMP);
                        paint.setShader(shader);
                        paint.setAntiAlias(true);
                        float r = size / 2f;
                        canvas.drawCircle(r, r, r, paint);
                        squaredBitmap.recycle();
                        return bitmap;
                    }

                    @Override
                    public String key() {
                        return "circle";
                    }
                };
                Picasso
                        .with(this)// 指定Context
                        .load(url) //指定图片URL
                        .transform(transform) // 指定图片转换器
                        .into(iv2); // 指定显示图片的ImageView

　　6:显示圆角图片

 //显示圆角图片
                class RoundedTransformation implements com.squareup.picasso.Transformation {
                    private final int radius;
                    private final int margin;  // dp

                    // radius is corner radii in dp
                    // margin is the board in dp
                    public RoundedTransformation(final int radius, final int margin) {
                        this.radius = radius;
                        this.margin = margin;
                    }

                    @Override
                    public Bitmap transform(final Bitmap source) {
                        final Paint paint = new Paint();
                        paint.setAntiAlias(true);
                        paint.setShader(new BitmapShader(source, Shader.TileMode.CLAMP, Shader.TileMode.CLAMP));

                        Bitmap output = Bitmap.createBitmap(source.getWidth(), source.getHeight(), Bitmap.Config.ARGB_8888);
                        Canvas canvas = new Canvas(output);
                        canvas.drawRoundRect(new RectF(margin, margin, source.getWidth() - margin, source.getHeight() - margin), radius, radius, paint);

                        if (source != output) {
                            source.recycle();
                        }

                        return output;
                    }

                    @Override
                    public String key() {
                        return "rounded(radius=" + radius + ", margin=" + margin + ")";
                    }
                }
                Picasso
                        .with(this)// 指定Context
                        .load(url) //指定图片URL
                        .transform(new RoundedTransformation(360,0)) // 指定图片转换器
                        .into(iv3); // 指定显示图片的ImageView

　　demo:http://download.csdn.net/detail/tom91/9631371