/**
 * Background Async task to load user profile picture from url
 */
private class LoadProfileImage extends AsyncTask<String, Void, RoundedBitmapDrawable> {
    ImageView profileImageView;

    public LoadProfileImage(ImageView profileImageView) {
        this.profileImageView = profileImageView;
    }

    protected RoundedBitmapDrawable doInBackground(String... urls) {
        String photoUrl = urls[0];
        RoundedBitmapDrawable profileRoundedDrawable = null;
        try {
            InputStream inputStream = new java.net.URL(photoUrl).openStream();
            Resources res = getResources();

            profileRoundedDrawable = RoundedBitmapDrawableFactory.create(res, inputStream);
            profileRoundedDrawable.setCircular(true);
        } catch (Exception e) {
            Log.e("Error", e.getMessage());
            e.printStackTrace();
        }
        return profileRoundedDrawable;
    }

    protected void onPostExecute(RoundedBitmapDrawable result) {
        profileImageView.setImageDrawable(result);
    }
}

科特林

import android.graphics.BitmapFactory
import android.os.Bundle
import android.support.v4.graphics.drawable.RoundedBitmapDrawableFactory
import kotlinx.android.synthetic.main.activity_main.*

val bitmap = BitmapFactory.decodeResource(resources, R.drawable.myImage)
val rounded = RoundedBitmapDrawableFactory.create(resources, bitmap)
rounded.cornerRadius = 20f
profileImageView.setImageDrawable(rounded)

为了使ImageView成为圆形，我们可以改变拐角半径:

rounded.isCircular = true

最近，还有另一种方法——使用Glide的生成API。它需要一些初始的工作，但它给了你Glide所有的力量，以及做任何事情的灵活性，因为你重写了实际的代码，所以我认为从长远来看，这是一个很好的解决方案。另外，使用非常简单和整洁。

首先，设置Glide版本4+:

implementation 'com.github.bumptech.glide:glide:4.6.1'
annotationProcessor 'com.github.bumptech.glide:compiler:4.6.1'

然后创建Glid的app模块类来触发注释处理:

@GlideModule
public final class MyAppGlideModule extends AppGlideModule {}

然后创建实际工作的Glide扩展。你可以自定义它来做任何你想做的事情:

@GlideExtension
public class MyGlideExtension {

    private MyGlideExtension() {}

    @NonNull
    @GlideOption
    public static RequestOptions roundedCorners(RequestOptions options, @NonNull Context context, int cornerRadius) {
        int px = Math.round(cornerRadius * (context.getResources().getDisplayMetrics().xdpi / DisplayMetrics.DENSITY_DEFAULT));
        return options.transforms(new RoundedCorners(px));
    }
}

添加这些文件之后，构建您的项目。

然后像这样在你的代码中使用它:

GlideApp.with(this)
        .load(imageUrl)
        .roundedCorners(getApplicationContext(), 5)
        .into(imageView);

虽然前两个答案是可行的，但我希望再多描述一点。 比如说，ImageView所在的地方有一个活动或片段。您希望绘制图像并按比例缩放。然后你应该在onCreate或onCreateView中写入如下代码:

LinearLayout rootLayout = (LinearLayout) findViewById(R.id.rootLayout);
ImageView image = (ImageView) findViewById(R.id.image);
// Wait till an activity is visible and image can be measured.
rootLayout.post(new Runnable() {
    @Override
    public void run() {
        // Setting ImageView height with aspect ratio.
        Drawable drawable = ContextCompat.getDrawable(getActivity(), R.drawable.your_image);
        int height = getImageViewHeight(drawable, image);

        // Rounding image corners.
        float radius = getResources().getDimension(R.dimen.your_radius_in_dp);
        Bitmap bitmap = ((BitmapDrawable) drawable).getBitmap();
        Bitmap result = getRoundedBitmap(bitmap, image.getWidth(), height, radius);
        image.setImageBitmap(result);
    }
});

其中设置新的图像高度为:

public static int getImageViewHeight(Drawable drawable, ImageView imageView) {
    imageView.setImageDrawable(drawable);
    int width = drawable.getIntrinsicWidth();
    int height = 0;
    if (width > 0) {
        height = (drawable.getIntrinsicHeight() * imageView.getWidth()) / width;
        imageView.getLayoutParams().height = height;
        imageView.requestLayout();
    }
    return height;
}

然后，您应该编写一个方法来缩放图像并使其圆角。这里的width和height是位图的新维度(更小或更大)。在下面的例子中，我只圆角上的两个角。

private Bitmap getRoundedBitmap(Bitmap bitmap, int width, int height, float radius) {
    // Create scaled bitmap.
    Bitmap scaledBitmap = Bitmap.createScaledBitmap(bitmap, width, height, false);
    BitmapShader shader = new BitmapShader(scaledBitmap, Shader.TileMode.CLAMP, Shader.TileMode.CLAMP);

    Paint paint = new Paint();
    paint.setAntiAlias(true);
    paint.setShader(shader);

    Bitmap result = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
    Canvas canvas = new Canvas(result);
    // First make all corners round.
    canvas.drawRoundRect(new RectF(0, 0, width, height), radius, radius, paint);
    // Then draw bottom rectangle.
    canvas.drawRect(0, height - radius, radius, height, paint);
    canvas.drawRect(width - radius, height - radius, width, height, paint);
    return result;
}

在glide库和RoundedBitmapDrawableFactory类的帮助下，很容易实现。您可能需要创建圆形占位符映像。

    Glide.with(context)
        .load(imgUrl)
        .asBitmap()
        .placeholder(R.drawable.placeholder)
        .error(R.drawable.placeholder)
        .into(new BitmapImageViewTarget(imgProfilePicture) {
            @Override
            protected void setResource(Bitmap resource) {
                RoundedBitmapDrawable drawable = RoundedBitmapDrawableFactory.create(context.getResources(),
                        Bitmap.createScaledBitmap(resource, 50, 50, false));
                drawable.setCornerRadius(10); //drawable.setCircular(true);
                imgProfilePicture.setImageDrawable(drawable);
            }
        });

你可以很容易地使用roundedImageView库:

compile 'com.makeramen:roundedimageview:2.3.0'

然后:

<com.makeramen.roundedimageview.RoundedImageView
  xmlns:app="http://schemas.android.com/apk/res-auto"
  android:id="@+id/img_episode"
  android:layout_width="wrap_content"
  android:layout_height="wrap_content"
  android:elevation="7dp"
  app:riv_border_color="@color/colorPrimary"
  app:riv_border_width="1dip"
  app:riv_corner_radius="10dip"
  app:riv_mutate_background="true"
  />