Error:Unable to resolve dependency for ':app@debug/compileClasspath': Could not resolve 问题解决

After trying a lot, involving many solutions on Baidu, I finally found the solution: see the difference. . . .
 

//这里是app里面的配置
buildTypes {
        debug {
              debuggable true
                ....
        }
        sdk {
                debuggable true
                minifyEnabled true
                shrinkResources false
                zipAlignEnabled true
                ....
        }
        release {
              minifyEnabled false
                ....
        }
    }

• /**
   * 这里是library的bulide.gradle配置
   */
   buildTypes {
        
          release {
              minifyEnabled false
              proguardFiles getDefaultProguardFile('proguard-android.txt'), 
              'proguard-rules.pro'
          }
  
      }

  Find the difference? Modify the build.gradle of the library and refer to the build.gradle in the app. For example (empty is also acceptable):

• /**
   * bulide.gradle的配置
   */
   buildTypes {
         debug {
  
          }
          sdk {
  
          }
        
          release {
              minifyEnabled false
              proguardFiles getDefaultProguardFile('proguard-android.txt'), 
              'proguard-rules.pro'
          }
  
      }

  Sync Now Recompile, solved.