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Embracing AGP 9 and JDK 21: A Gradual Path to Android Build Optimization

Last updated : 2026-02-01 19:32

As Android developers, major AGP (Android Gradle Plugin) updates are always significant. AGP 9 in particular promises a stricter, faster build environment, moving away from ambiguous configurations.

Instead of waiting for its full release and then scrambling to fix issues, why not start preparing your project now, gradually aligning it with "AGP 9 standards" through your gradle.properties file?

🤔 Why JDK 21 and AGP 9 Now? (The Ultimate Synergy)

When transitioning to AGP 9, updating to JDK 21 isn't just a "requirement"; it's a powerful "booster" that dramatically enhances your development experience.

Performance Synchronization: JDK 21's improved resource management, including features like Virtual Threads, allows Gradle to fully leverage its parallel build capabilities, leading to more stable and efficient builds.
Language Specification Alignment: By targeting Java 21, you bridge potential gaps in type inference and bytecode generation in mixed Java/Kotlin projects, especially as Kotlin 2.x gains traction.
Precision R8 Optimization: AGP 9 is optimized to parse and transform class files generated by JDK 21. This means that even with stricter settings, R8 can more accurately understand modern code structures, reducing the need for excessive keep rules while safely shrinking code.

This combination offers the kind of seamless experience you get from pairing the latest OS with the latest CPU.

🤔 Prepare with `gradle.properties`: 10 Flags to Enable Today

The strategy is simple: enable one flag at a time, fix any errors that arise, and then move to the next. This iterative approach is the most reliable way to prepare for AGP 9.

1. Structure Enforcement (Clean Up Your Project)

android.uniquePackageNames=true: Prevents duplicate package names across modules, eliminating resource conflicts.
android.usesSdkInManifest.disallowed=true: Enforces placing minSdk, targetSdk, etc., in build.gradle instead of AndroidManifest.xml.
android.defaults.buildfeatures.resvalues=true: Explicitly controls the generation of resValue entries.

2. Build Speed Enhancements

android.enableAppCompileTimeRClass=true: Uses lightweight R classes during app compilation, significantly improving build times for large projects.
android.sdk.defaultTargetSdkToCompileSdkIfUnset=true: Automatically sets targetSdk to compileSdk if unspecified, preventing inconsistent behavior.
android.dependency.useConstraints=true: Utilizes Gradle's "Constraints" feature for dependency resolution, making library version management more robust.

3. Aggressive R8 / Optimization Settings (The Biggest Hurdle)

android.r8.strictFullModeForKeepRules=true: Enables R8's Full Mode. This maximizes optimization but requires precise keep rules for code that relies on reflection, potentially leading to crashes if not handled correctly.
android.r8.optimizedResourceShrinking=true: Employs a more advanced algorithm for removing unused resources, leading to smaller app sizes.

4. Next-Gen Defaults

android.builtInKotlin=true: Prioritizes AGP's built-in Kotlin support.
android.newDsl=false: Use this to maintain the current DSL while preparing for future changes.

🤔 Conclusion: One Flag at a Time for a Smoother Future

The AGP 9 update is akin to a major cleanup. Attempting it all at once can be overwhelming, but tackling it gradually makes it incredibly rewarding.

Why not start with android.uniquePackageNames=true? With each flag you enable, your project will move closer to a more modern, robust, and efficient build environment.

👉 AGP 9.0 移行ガイド：新旧コード比較で見るモダンビルド設定

Why are updates to Kotlin, Compose, and KSP such a hassle?

Last updated : 2025-11-13 10:09

In Android development, you're constantly dealing with the same set of three: Kotlin, the Compose Compiler, and KSP.

They seem like a friendly group, but their update schedules are always completely different! You upgrade Kotlin, and the Compose Compiler isn't compatible. You change something, and KSP throws a build error because of an internal API change...

To better manage this "dependency triangle" situation, the main idea is to use Renovate's configuration to treat them as a single unit. The simple plan is: "Raise all Kotlin ecosystem dependencies at the same time!"

🧑🏻‍💻 Brief overview of the renovate.json file


{
  "$schema": "https://docs.renovatebot.com/renovate-schema.json",
  "extends": [
    "config:base",
    "group:all",
    ":dependencyDashboard",
    "schedule:daily"
  ],
  "baseBranches": ["main"],
  "commitMessageExtra": "{{{currentValue}}} to {{#if isPinDigest}}{{{newDigestShort}}}{{else}}{{#if isMajor}}{{prettyNewMajor}}{{else}}{{#if isSingleVersion}}{{prettyNewVersion}}{{else}}{{#if newValue}}{{{newValue}}}{{else}}{{{newDigestShort}}}{{/if}}{{/if}}{{/if}}{{/if}}",
  "packageRules": [
    {
      "matchPackagePatterns": ["androidx.compose.compiler:compiler"],
      "groupName": "kotlin"
    },
    {
      "matchPackagePatterns": ["org.jetbrains.kotlin.*"],
      "groupName": "kotlin"
    },
    {
      "matchPackagePatterns": ["com.google.devtools.ksp"],
      "groupName": "kotlin"
    }
  ]
}

👉 architecture-samples/renovate.json at main · android/architecture-samples

Roughly summarized, here are the key points:

groupName: "kotlin" to bundle dependencies This setting specifies that the three elements—the Compose Compiler, Kotlin, and KSP—should be treated as belonging to the "same group." This allows Renovate to update them all together at once.
schedule: daily for a calm update pace This checks for updates once a day. You'll receive pull requests (PRs) on a daily basis, preventing a huge influx of dependency updates all at once, which makes things much easier to manage.
commitMessageExtra to see changes at a glance The version difference, like "2.0.10 → 2.0.20," is automatically added to the PR title. It's a small tweak, but surprisingly useful.

Setting up your configuration this way significantly reduces the tragedy of "Kotlin got updated, but Compose broke..."

🧑🏻‍💻 What We Found While Using It

Once this setup is in place, you can feel much more confident testing updates for everything Kotlin-related. Renovate diligently checks daily, automatically creating a PR whenever a new version drops.

But there's one small warning:

The Compose Compiler sometimes takes a little extra time to catch up to the latest Kotlin version. So, don't just merge the PR when you see it—it's highly recommended to verify the CI status first.

KSP is similar; because it depends on Kotlin's internal workings, it's safer to update it along with Kotlin and run your tests together.

🧑🏻‍💻 Summary: Teach Renovate that "These Three Are a Set"

The configuration we discussed treats the trio of Kotlin, the Compose Compiler, and KSP as a single group.

Bundle all Kotlin-related dependencies for simultaneous updates.
Check for updates at a manageable daily pace.
See version differences directly in the PR title.

Just implementing this significantly reduces the problems caused by versions getting out of sync and breaking your build.

💡 Key Takeaway: Use Renovate less as an "automatic update tool" and more as a "dependency rulebook."

We simply need to tell Kotlin, Compose, and KSP to cooperate and "work together."

👉 Kotlin・Compose・KSP の更新、どうしてこんなに面倒なの?

Checking Your Cable Specs: The Secret Lies in the Wires

Last updated : 2025-11-08 06:03

When connecting your smartphone or development device to your computer, have you ever thought,

“Why is the transfer so slow?” or “Why am I getting connection warnings?”

One often overlooked cause is the cable’s specifications. Even if two USB cables look identical, their internal structure and supported standards can make a huge difference.

This time, I tried using a USB cable tester to see how we can easily check a cable’s actual specs.

🤔 What You Can Learn with the Treedix USB Cable Tester

The tool I used is the Treedix USB Cable Tester Board, which supports multiple connector types such as USB-A, Type-C, and Micro-B.
It can test both data transfer and charging performance — a very handy little board.

👉 Treedix USB ケーブルテスターボード USB ケーブルチェッカーデータワイヤ充電テストデータラインタイプ C – Treedix Official

👉 TREEDIX USB Cable Tester Manual - Test USB Cables for Charging and Data Transfer

According to its manual, if the LEDs for “High-Speed Charging” and “High-Speed Data” light up, it means the cable supports USB 3.x.

If they don’t light up, the cable is only USB 2.0 level.

In short, this tiny board lets you instantly “see” the invisible differences inside your cables.

🤔 Test Results: USB 2.0 vs USB 3.x

First, I tested the cable I had been using regularly — and it turned out to be USB 2.0.
Apparently, it was almost a charging-only cable with no proper data lines.

Next, I tested a recently purchased Buffalo cable. This time, the USB 3.x indicators lit up clearly, confirming that it supports high-speed data transfer.

When I switched to this cable for connecting my Android device to Android Studio, the connection warnings disappeared completely — the link became much more stable.

👉 Amazon.co.jp: バッファロー BUFFALO USB3.1 Gen2ケーブル(C to C) PD3A 1.0m ブラック【 iPhone 17 / 17 pro 動作確認済み】 BSUCC312P3A10BK : パソコン・周辺機器

However, I didn’t feel much difference in actual transfer speed, suggesting that other factors (like device or build performance) may be the real bottleneck.