This is the third article in the Android App ANR series, focusing on real-world ANR cases. The series includes:
This is the second article in the Android App ANR series, focusing on ANR analysis methodology and key logs. The series includes:
Jank, slow response, and ANRs can share causes or occur together, but they are not three severity levels of the same problem. When a user says an app feels slow, first distinguish uneven animation, a long delay after an action, and a system-detected failure to respond.
Animation and scrolling stutter is usually called jank. Long startup, screen wake-up, or navigation delays are slow response / high latency. An ANR depends on a specific system timeout condition. Frame-drop rate, startup duration, and ANR rate measure different things.
This is the third article in the Responsiveness series, focusing on extended knowledge when using Systrace to analyze app responsiveness, including startup speed testing, log interpretation, state analysis, and third-party startup libraries.
On Medium, @MindOrks published a 2020 Android Developer Learning Path. Given that some readers may have difficulty accessing the original content, I am sharing it here combined with my own 2020 learning plan for your reference.
The original article is quite simple, mostly listing knowledge points without much explanation. I have added brief introductions for each point and included some additional topics based on my own understanding. This is for your reference only.
This article is primarily for Android developers. If you are a beginner, it will help you find a learning path. If you are an experienced developer, it can help you identify gaps in your knowledge. If you have any other suggestions, feel free to leave a message.
Finding a value in an unsorted array or linked list without an additional index can require scanning every element. A hash table uses a hash to locate a bucket and supports constant-time basic lookup when hashes are well distributed; it does not guarantee O(1) lookup for every input.
HashMap is an implementation of the Map interface based on a hash table. This implementation provides all optional mapping operations and permits null values and null keys. (The HashMap class is roughly equivalent to Hashtable, except that it is unsynchronized and permits nulls.) This class makes no guarantees as to the order of the map; in particular, it does not guarantee that the order will remain constant over time.
This article follows the source through the array-and-list structure, constructors, put and resizing, get, and the iterator checks using modCount. A final section covers changes in later JDKs.
The Singleton pattern restricts how instances are created and accessed. This article follows eager initialization, double-checked locking, the holder idiom, and enums, explaining their initialization behavior and limits.
Technical review (2026-10-13): These patterns remain applicable. The discussion is checked against the Java 5+ memory model and Java SE 25 specifications. It corrects the loading/initialization distinction, runtime access checks, and the explanation of enum reflection. The code blocks named
Singletonare alternatives, not declarations to combine in one source file.