但是有时候会出现各种不明情况的报错，最常见的一种原因就是依赖项版本冲突。
每个模块都可能依赖其他模块，这些模块又会依赖别的模块。而一个项目中的多个模块，对同一个模块的不同版本有依赖，就可能产生冲突。
通过gradle命令查看依赖树，可以比较直观的看到冲突。具体方法是在模块所在的目录，也即build.gradle所在目录下执行gradle dependencies（需要将gradle加入PATH环境变量），执行结果如图。
Transitive
Transitive用于自动处理子依赖项。默认为true，gradle自动添加子依赖项，形成一个多层树形结构；设置为false，则需要手动添加每个依赖项。
案例
以安卓单元测试espresso的配置为例，gradle依赖如下：
dependencies {
androidTestCompile('com.android.support.test:runner:0.2')
androidTestCompile('com.android.support.test:rules:0.2')
androidTestCompile('com.android.support.test.espresso:espresso-core:2.1')
}
运行gradle dependencies的结果如下。可以看到每个包的依赖项都被递归分析并添加进来。
+--- com.android.support.test:runner:0.2
| +--- junit:junit-dep:4.10
| | \--- org.hamcrest:hamcrest-core:1.1
| +--- com.android.support.test:exposed-instrumentation-api-publish:0.2
| \--- com.android.support:support-annotations:22.0.0
+--- com.android.support.test:rules:0.2
| \--- com.android.support.test:runner:0.2 (*)
\--- com.android.support.test.espresso:espresso-core:2.1
+--- com.android.support.test:rules:0.2 (*)
+--- com.squareup:javawriter:2.1.1
+--- org.hamcrest:hamcrest-integration:1.1
| \--- org.hamcrest:hamcrest-core:1.1
+--- com.android.support.test.espresso:espresso-idling-resource:2.1
+--- org.hamcrest:hamcrest-library:1.1
| \--- org.hamcrest:hamcrest-core:1.1
+--- javax.inject:javax.inject:1
+--- com.google.code.findbugs:jsr305:2.0.1
+--- com.android.support.test:runner:0.2 (*)
+--- javax.annotation:javax.annotation-api:1.2
\--- org.hamcrest:hamcrest-core:1.1
统一指定transitive
可以给dependencies统一指定transitive为false，再次执行dependencies可以看到如下结果。
configurations.all {
transitive = false
}
dependencies {
androidTestCompile('com.android.support.test:runner:0.2')
androidTestCompile('com.android.support.test:rules:0.2')
androidTestCompile('com.android.support.test.espresso:espresso-core:2.1')
}
+--- com.android.support.test:runner:0.2
+--- com.android.support.test:rules:0.2
\--- com.android.support.test.espresso:espresso-core:2.1
单独指定依赖项的transitive
dependencies {
androidTestCompile('com.android.support.test:runner:0.2')
androidTestCompile('com.android.support.test:rules:0.2')
androidTestCompile('com.android.support.test.espresso:espresso-core:2.1') {
transitive = false
}
}
版本冲突
在同一个配置下（例如androidTestCompile），某个模块的不同版本同时被依赖时，默认使用最新版，gradle同步时不会报错。例如下面的hamcrest-core和runner。
dependencies {
androidTestCompile('com.android.support.test:runner:0.4')
androidTestCompile('com.android.support.test:rules:0.2')
androidTestCompile('com.android.support.test.espresso:espresso-core:2.1')
}
+--- com.android.support.test:runner:0.4
| +--- com.android.support:support-annotations:23.0.1
| +--- junit:junit:4.12
| | \--- org.hamcrest:hamcrest-core:1.3
| \--- com.android.support.test:exposed-instrumentation-api-publish:0.4
+--- com.android.support.test:rules:0.2
| \--- com.android.support.test:runner:0.2 -> 0.4 (*)
\--- com.android.support.test.espresso:espresso-core:2.1
+--- com.android.support.test:rules:0.2 (*)
+--- com.squareup:javawriter:2.1.1
+--- org.hamcrest:hamcrest-integration:1.1
| \--- org.hamcrest:hamcrest-core:1.1 -> 1.3
+--- com.android.support.test.espresso:espresso-idling-resource:2.1
+--- org.hamcrest:hamcrest-library:1.1
| \--- org.hamcrest:hamcrest-core:1.1 -> 1.3
+--- javax.inject:javax.inject:1
+--- com.google.code.findbugs:jsr305:2.0.1
+--- com.android.support.test:runner:0.2 -> 0.4 (*)
+--- javax.annotation:javax.annotation-api:1.2
\--- org.hamcrest:hamcrest-core:1.1 -> 1.3
Force
force强制设置某个模块的版本。
configurations.all {
resolutionStrategy {
force 'org.hamcrest:hamcrest-core:1.3'
}
}
dependencies {
androidTestCompile('com.android.support.test:runner:0.2')
androidTestCompile('com.android.support.test:rules:0.2')
androidTestCompile('com.android.support.test.espresso:espresso-core:2.1')
}
可以看到，原本对hamcrest-core 1.1的依赖，全部变成了1.3。
+--- com.android.support.test:runner:0.2
| +--- junit:junit-dep:4.10
| | \--- org.hamcrest:hamcrest-core:1.1 -> 1.3
| +--- com.android.support.test:exposed-instrumentation-api-publish:0.2
| \--- com.android.support:support-annotations:22.0.0
+--- com.android.support.test:rules:0.2
| \--- com.android.support.test:runner:0.2 (*)
\--- com.android.support.test.espresso:espresso-core:2.1
+--- com.android.support.test:rules:0.2 (*)
+--- com.squareup:javawriter:2.1.1
+--- org.hamcrest:hamcrest-integration:1.1
| \--- org.hamcrest:hamcrest-core:1.1 -> 1.3
+--- com.android.support.test.espresso:espresso-idling-resource:2.1
+--- org.hamcrest:hamcrest-library:1.1
| \--- org.hamcrest:hamcrest-core:1.1 -> 1.3
+--- javax.inject:javax.inject:1
+--- com.google.code.findbugs:jsr305:2.0.1
+--- com.android.support.test:runner:0.2 (*)
+--- javax.annotation:javax.annotation-api:1.2
\--- org.hamcrest:hamcrest-core:1.1 -> 1.3
Exclude
Exclude可以设置不编译指定的模块
configurations {
all*.exclude group: 'org.hamcrest', module: 'hamcrest-core'
}
dependencies {
androidTestCompile('com.android.support.test:runner:0.2')
androidTestCompile('com.android.support.test:rules:0.2')
androidTestCompile('com.android.support.test.espresso:espresso-core:2.1')
}
+--- com.android.support.test:runner:0.2
| +--- junit:junit-dep:4.10
| +--- com.android.support.test:exposed-instrumentation-api-publish:0.2
| \--- com.android.support:support-annotations:22.0.0
+--- com.android.support.test:rules:0.2
| \--- com.android.support.test:runner:0.2 (*)
\--- com.android.support.test.espresso:espresso-core:2.1
+--- com.android.support.test:rules:0.2 (*)
+--- com.squareup:javawriter:2.1.1
+--- org.hamcrest:hamcrest-integration:1.1
+--- com.android.support.test.espresso:espresso-idling-resource:2.1
+--- org.hamcrest:hamcrest-library:1.1
+--- javax.inject:javax.inject:1
+--- com.google.code.findbugs:jsr305:2.0.1
+--- com.android.support.test:runner:0.2 (*)
\--- javax.annotation:javax.annotation-api:1.2
单独使用group或module参数
exclude后的参数有group和module，可以分别单独使用，会排除所有匹配项。例如下面的脚本匹配了所有的group为’com.android.support.test’的模块。
configurations {
all*.exclude group: 'com.android.support.test'
}
dependencies {
androidTestCompile('com.android.support.test:runner:0.2')
androidTestCompile('com.android.support.test:rules:0.2')
androidTestCompile('com.android.support.test.espresso:espresso-core:2.1')
}
\--- com.android.support.test.espresso:espresso-core:2.1
+--- com.squareup:javawriter:2.1.1
+--- org.hamcrest:hamcrest-integration:1.1
| \--- org.hamcrest:hamcrest-core:1.1
+--- com.android.support.test.espresso:espresso-idling-resource:2.1
+--- org.hamcrest:hamcrest-library:1.1
| \--- org.hamcrest:hamcrest-core:1.1
+--- javax.inject:javax.inject:1
+--- com.google.code.findbugs:jsr305:2.0.1
+--- javax.annotation:javax.annotation-api:1.2
\--- org.hamcrest:hamcrest-core:1.1
单独给某个模块指定exclude
dependencies {
androidTestCompile('com.android.support.test:runner:0.2')
androidTestCompile('com.android.support.test:rules:0.2')
androidTestCompile('com.android.support.test.espresso:espresso-core:2.1') {
exclude group: 'org.hamcrest'
}
}
+--- com.android.support.test:runner:0.2
| +--- junit:junit-dep:4.10
| | \--- org.hamcrest:hamcrest-core:1.1
| +--- com.android.support.test:exposed-instrumentation-api-publish:0.2
| \--- com.android.support:support-annotations:22.0.0
+--- com.android.support.test:rules:0.2
| \--- com.android.support.test:runner:0.2 (*)
\--- com.android.support.test.espresso:espresso-core:2.1
+--- com.android.support.test:rules:0.2 (*)
+--- com.squareup:javawriter:2.1.1
+--- com.android.support.test.espresso:espresso-idling-resource:2.1
+--- javax.inject:javax.inject:1
+--- com.google.code.findbugs:jsr305:2.0.1
+--- com.android.support.test:runner:0.2 (*)
\--- javax.annotation:javax.annotation-api:1.2
不同配置下的版本冲突
同样的配置下的版本冲突，会自动使用最新版；而不同配置下的版本冲突，gradle同步时会直接报错。可使用exclude、force解决冲突。
例如compile 'com.android.support:appcompat-v7:23.1.1'，和androidTestCompile 'com.android.support.test.espresso:espresso-core:2.1'，所依赖的com.android.support:support-annotations版本不同，就会导致冲突。
dependencies {
compile 'com.android.support:appcompat-v7:23.1.1'
androidTestCompile('com.android.support.test:runner:0.2')
androidTestCompile('com.android.support.test:rules:0.2')
androidTestCompile('com.android.support.test.espresso:espresso-core:2.1')
}
gradle同步时会提示
Warning:Conflict with dependency 'com.android.support:support-annotations'. Resolved versions for app and test app differ.
执行dependencies会提示
FAILURE: Build failed with an exception.
* What went wrong:
A problem occurred configuring project ':app'.
> Conflict with dependency 'com.android.support:support-annotations'. Resolved versions for app and test app differ.
* Try:
Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output.
BUILD FAILED
不兼容
虽然可以通过force、exclude等方式避免依赖项版本冲突，使得grade同步成功，但是并不能代表编译时没有问题。由于不同版本可能不完全兼容，于是会出现各种奇怪的报错。已知的解决思路是更改包的版本、尝试强制使用不同版本的依赖项，找到可兼容的依赖组合。
报错例如：
com.android.dex.DexException: Multiple dex files define Lorg/hamcrest/MatcherAssert;
at com.android.dx.merge.DexMerger.readSortableTypes(DexMerger.java:596)
at com.android.dx.merge.DexMerger.getSortedTypes(DexMerger.java:554)
at com.android.dx.merge.DexMerger.mergeClassDefs(DexMerger.java:535)
at com.android.dx.merge.DexMerger.mergeDexes(DexMerger.java:171)
at com.android.dx.merge.DexMerger.merge(DexMerger.java:189)
at com.android.dx.command.dexer.Main.mergeLibraryDexBuffers(Main.java:454)
at com.android.dx.command.dexer.Main.runMonoDex(Main.java:303)
at com.android.dx.command.dexer.Main.run(Main.java:246)
at com.android.dx.command.dexer.Main.main(Main.java:215)
at com.android.dx.command.Main.main(Main.java:106)
Error:Execution failed for task ':app:dexDebugAndroidTest'.
> com.android.ide.common.process.ProcessException: org.gradle.process.internal.ExecException: Process 'command '/Library/Java/JavaVirtualMachines/jdk1.8.0_40.jdk/Contents/Home/bin/java'' finished with non-zero exit value 2
BUILD FAILED
又例如Android执行Espresso单元测试时出现：
Running tests
Test running started
java.lang.NoSuchMethodError: org.hamcrest.core.AnyOf.anyOf
at org.hamcrest.Matchers.anyOf(Matchers.java:87)
at android.support.test.espresso.Espresso.
at com.jzj1993.unittest.test.MainActivityEspressoTest.sayHello(MainActivityEspressoTest.java:28)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:525)
at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:45)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:15)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:42)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:20)
at android.support.test.internal.statement.UiThreadStatement.evaluate(UiThreadStatement.java:55)
at android.support.test.rule.ActivityTestRule$ActivityStatement.evaluate(ActivityTestRule.java:257)
at org.junit.rules.RunRules.evaluate(RunRules.java:18)
at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:263)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:68)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:47)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:231)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:60)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:229)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:50)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:222)
at org.junit.runners.ParentRunner.run(ParentRunner.java:300)
at org.junit.runners.Suite.runChild(Suite.java:128)
at org.junit.runners.Suite.runChild(Suite.java:24)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:231)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:60)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:229)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:50)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:222)
at org.junit.runners.ParentRunner.run(ParentRunner.java:300)
at org.junit.runner.JUnitCore.run(JUnitCore.java:157)
at org.junit.runner.JUnitCore.run(JUnitCore.java:136)
at android.support.test.internal.runner.TestExecutor.execute(TestExecutor.java:54)
at android.support.test.runner.AndroidJUnitRunner.onStart(AndroidJUnitRunner.java:228)
at android.app.Instrumentation$InstrumentationThread.run(Instrumentation.java:1701)
Finish
参考资料与扩展阅读
https://docs.gradle.org/current/userguide/dependency_management.html
http://www.concretepage.com/build-tools/gradle/gradle-exclude-transitive-dependency-example
最后，欢迎扫码关注微信公众号。
本文由jzj1993原创，转载请注明来源：http://www.paincker.com/gradle-dependencies