Hey there, let’s break down exactly why your app is having trouble running on Android 4.4 and older OS versions, using the dependency config you shared:

1. Android Support Library 26.x.x Gotchas #

You’re using com.android.support:appcompat-v7:26.+ and com.android.support:design:26.+ — these libraries technically support down to Android 4.0 (API 14), so Android 4.4 (API 19) should be in the clear, right? Well, not so fast:

• If your project’s compileSdkVersion isn’t set to 26 or higher, you’ll hit compile-time compatibility errors that prevent the app from working on older devices.
• Using the 26.+ wildcard version is risky too — it can pull in unexpected minor updates that might introduce hidden compatibility bugs with API 19.

2. Google Play Services Ads 9.4.0 is the Big Culprit #

This is likely the main issue. com.google.android.gms:play-services-ads:9.4.0 is part of Google Play Services 9.x, which has two key problems for Android 4.4:

• While it technically supports down to Android 4.1 (API 16), this specific version has known compatibility bugs on API 19 devices, especially on devices with outdated Google Play Services.
• If your project’s targetSdkVersion is set to 23 or higher, the Ads library might try to use runtime permissions — a feature that didn’t exist on Android 4.4. This will cause crashes when the app tries to request permissions that aren’t supported.

3. Don’t Overlook Your Project’s Core Configs #

Beyond dependencies, double-check your module-level build.gradle file for these critical settings:

• minSdkVersion: If this is set to anything higher than 19, your app will be automatically blocked from installing on Android 4.4 devices. Make sure it’s set to 19 or lower.
• compileSdkVersion: For Support Library 26.x.x, this must be set to 26 — mismatched versions here break compatibility across Android versions.
• targetSdkVersion: Stick to 23 if you want to avoid runtime permission headaches on pre-6.0 devices like Android 4.4.

Fixes to Get Your App Running on Android 4.4 #

Here’s what you can do to resolve the issues:

• Update the Ads Library: Swap com.google.android.gms:play-services-ads:9.4.0 for a version that’s more stable on API 19, like 17.0.0 (it supports down to API 14 and has better backward compatibility).
• Lock in Support Library Versions: Replace 26.+ with a specific version like 26.1.0 to avoid unexpected updates breaking things.
• Tweak Your Build Configs: Ensure minSdkVersion=19, compileSdkVersion=26, and targetSdkVersion=23 in your module build.gradle.
• Check for Dependency Conflicts: Run ./gradlew dependencies (Windows: gradlew.bat dependencies) to spot any conflicting library versions — mismatched support libraries often cause silent crashes on older devices.

Here’s an example of your adjusted dependencies:

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    androidTestCompile('com.android.support.test.espresso:espresso-core:2.2.2', { 
        exclude group: 'com.android.support', module: 'support-annotations' 
    })
    compile 'com.android.support:appcompat-v7:26.1.0'
    compile 'com.android.support:design:26.1.0'
    compile 'com.android.support.constraint:constraint-layout:1.0.2'
    compile 'com.google.android.gms:play-services-ads:17.0.0'
    testCompile 'junit:junit:4.12'
}

One last tip: Test your app on an actual Android 4.4 device or emulator, and check Logcat for specific errors like NoSuchMethodError or ClassNotFoundException — these will point you directly to the exact code causing the compatibility issue.

内容的提问来源于stack exchange，提问作者NAGENDRA KUMAR KAIRI