android - gradle - library duplicates in dependencies -

i have android project gradle. problem is: in project view see few versions of support-v4 libraries, example support-v4-21.0.3 , support-v4-22.2.0.

but in build.gradle don't have support-v4 @ all.

but have ~10 other dependencies in build.gradle. example appcompat-v7:22.2.0. can suggests appcompat-v7:22.2.0 depens on support-v4-22.2.0 in maven dependencies , implicitly pulls it. have no ideas pulls support-v4-21.0.3.

as far know libs packed in apk , increase weight of apk.

so have next questions:

1. how avoid library duplicates?
2. how see maven dependencies in android studio?
3. how detect library require library? example library require support-v4-21.0.3 in project?

to find duplicate dependencies or required dependencies, can visualize library dependencies in tree. execute gradle command below.

gradle -q dependencies yourproject:dependencies --configuration compile 

note that, run gradlew in windows below.

gradlew -q dependencies yourproject:dependencies --configuration compile 

the command result show human-readable tree hierarchy of dependencies below.

compile - classpath compiling main sources. +--- org.androidannotations:androidannotations-api:3.2 +--- com.android.support:support-annotations:22.1.1 +--- com.squareup:otto:1.3.6 +--- in.srain.cube:grid-view-with-header-footer:1.0.10 +--- com.nostra13.universalimageloader:universal-image-loader:1.9.3 +--- com.github.chrisbanes.photoview:library:1.2.3 +--- org.simpleframework:simple-xml:2.7.1 +--- com.google.android.gms:play-services-base:6.5.+ -> 6.5.87 +--- project :yourproject |    +--- com.loopj.android:android-async-http:1.4.6 |    +--- org.apache.httpcomponents:httpmime:4.2.5 |    |    \--- org.apache.httpcomponents:httpcore:4.2.4 |    \--- com.google.code.gson:gson:2.3.1 +--- project :facebook |    \--- com.android.support:appcompat-v7:22.1.1 |         \--- com.android.support:support-v4:22.1.1 |              \--- com.android.support:support-annotations:22.1.1 -> 22.2.0 

you can see overriden dependencies , decide in mind ones should avoided. in above example, last line com.android.support:support-annotations presents overriden 22.1.1 22.2.0 internally.

to avoid duplicates, can add exclude clauses in each project build.gradle file.

compile('com.github.chrisbanes.photoview:library:1.2.3') {     exclude group: 'com.android.support' } compile('org.simpleframework:simple-xml:2.7.1') {     exclude module: 'stax'     exclude module: 'stax-api'     exclude module: 'xpp3' } compile('com.google.android.gms:play-services-base:6.5.+')         {             exclude module: 'support-v4'         } 

for more information, can see tutorial @ https://docs.gradle.org/current/userguide/userguide_single.html#sec:listing_dependencies