Comprehensive Guide to Glide Image Loading Process and Configuration in Android

Introduction

This tutorial explains the basic usage of Glide 4.11, starting with adding the dependency and calling the three core methods with() , load() , and into() .

Four‑Step Decode Task Startup

The process from into() to launching DecodeJob involves four objects: Request, Target, Engine, and DecodeJob.

Request

Request is built by RequestBuilder and managed by RequestManager , which binds lifecycle, monitors network, creates request builders, and starts requests.

Target

Targets convert views into loadable targets; common implementations include ImageViewTarget , RequestFutureTarget , and various custom targets for preloading, widgets, GIFs, and notifications.

Engine

The Engine handles loading, key generation, resource recycling, and disk cache provision. Its load() method first checks memory cache, then starts a new EngineJob and DecodeJob if needed.

DecodeJob

DecodeJob runs on a thread pool and executes based on three run reasons (INITIALIZE, SWITCH_TO_SOURCE_SERVICE, DECODE_DATA). It progresses through six stages: INITIALIZE, RESOURCE_CACHE, DATA_CACHE, SOURCE, ENCODE, and FINISH, using three data generators (SourceGenerator, DataCacheGenerator, ResourceCacheGenerator).

Six‑Step Image Loading Flow

The flow consists of Model (source), Data (raw), Resource (decoded), TransformedResource, TranscodedResource, and Target, with components such as ModelLoader, ResourceDecoder, Transformation, ResourceTranscoder, and ResourceEncoder handling each step.

Glide Caching Principles

Glide uses a three‑level cache: memory, disk, and source. Memory cache is implemented by LruResourceCache , disk cache by DiskLruCacheWrapper , and various DiskCacheStrategy options (AUTOMATIC, ALL, NONE, RESOURCE, DATA) control what is cached.

Initialization and Configuration

Glide initialization occurs via Glide.with() and initializeGlide() , reading AppGlideModule settings through a generated module. The Registry holds ModelLoaders, Encoders, Decoders, etc., which can be replaced in registerComponents() . GlideBuilder configures thread pools, memory size calculator, bitmap pool, array pool, and other components.

Thread Pools

Four thread pools are provided: SourceExecutor, UnlimitedSourceExecutor, DiskCacheExecutor, and AnimationExecutor, each configurable via GlideExecutor.Builder .

Memory Size Calculator

Calculates sizes for BitmapPool, ArrayPool, and MemoryCache based on screen size and a multiplier (default 0.4 of the app’s memory class).

Glide Image Loading Options

Extensive options include placeholders, error/fallback images, size overrides, scaling methods (fitCenter, centerCrop, centerInside), transformations, cache controls, priority, size multiplier, encoding format/quality, frame extraction, decode format, timeout, transition animations, listeners, and request types such as asBitmap() , asFile() , submit() , downloadOnly() , and preload() .