didi/DoKit · error · IllegalArgumentException

Transformation list must not be null.

Error message

Transformation list must not be null.

What it means

Thrown by the list overload of Request.Builder.transform(List<? extends Transformation>) when the list argument is null. Picasso rejects the null list up front (the per-element transform(Transformation) overload separately validates each entry).

Source

Thrown at Android/dokit/src/main/java/com/didichuxing/doraemonkit/picasso/Request.java:446

      }
      if (transformation.key() == null) {
        throw new IllegalArgumentException("Transformation key must not be null.");
      }
      if (transformations == null) {
        transformations = new ArrayList<com.didichuxing.doraemonkit.picasso.Transformation>(2);
      }
      transformations.add(transformation);
      return this;
    }

    /**
     * Add a list of custom transformations to be applied to the image.
     * <p>
     * Custom transformations will always be run after the built-in transformations.
     */
    public Builder transform(List<? extends Transformation> transformations) {
      if (transformations == null) {
        throw new IllegalArgumentException("Transformation list must not be null.");
      }
      for (int i = 0, size = transformations.size(); i < size; i++) {
        transform(transformations.get(i));
      }
      return this;
    }

    /** Create the immutable {@link Request} object. */
    public Request build() {
      if (centerInside && centerCrop) {
        throw new IllegalStateException("Center crop and center inside can not be used together.");
      }
      if (centerCrop && (targetWidth == 0 && targetHeight == 0)) {
        throw new IllegalStateException(
            "Center crop requires calling resize with positive width and height.");
      }
      if (centerInside && (targetWidth == 0 && targetHeight == 0)) {
        throw new IllegalStateException(

View on GitHub (pinned to 626827cddb)

Solutions

1. Return Collections.emptyList() instead of null from transformation-builder helpers.
2. Null-check or default the list before calling: transform(list != null ? list : Collections.emptyList()).
3. In Kotlin, make transformation lists non-null (List<Transformation> instead of List<Transformation>?).

Example fix

// before
List<Transformation> ts = settings.enabled() ? getTransforms() : null;
builder.transform(ts);

// after
List<Transformation> ts = settings.enabled() ? getTransforms() : Collections.emptyList();
builder.transform(ts);

List<Transformation> safe = transformations != null ? transformations : Collections.<Transformation>emptyList();
builder.transform(safe);

static List<Transformation> nonNullTransforms(List<Transformation> list) {
  return list != null ? list : Collections.<Transformation>emptyList();
}

When it happens

Trigger: Calling transform((List<Transformation>) null), or transform(buildTransforms()) where buildTransforms() returned null.

Common situations: A helper that returns null instead of an empty list when no transformations apply; Java varargs passing a null array; Kotlin code passing a nullable List<Transformation>! from Java interop.

Related errors

• uri == null
• path == null
• file == null
• Priority invalid.
• Transformation must not be null.

AI-assisted analysis of didi/DoKit@626827cddb (2026-08-14). Data as JSON: /api/errors/db32e80348fdb3d2. Report an issue: GitHub.