Unable to resolve dependency for ':app@debug/compileClasspath': Could not find any version that...

新建Android项目打开后，报如下的错

Unable to resolve dependency for ':app@debug/compileClasspath': Could not find any version that matches com.android.support:appcompat-v7:29.+.
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Unable to resolve dependency for ':app@debugAndroidTest/compileClasspath': Could not find any version that matches com.android.support:appcompat-v7:29.+.
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Unable to resolve dependency for ':app@debugUnitTest/compileClasspath': Could not find any version that matches com.android.support:appcompat-v7:29.+.
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Unable to resolve dependency for ':app@release/compileClasspath': Could not find any version that matches com.android.support:appcompat-v7:29.+.
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Unable to resolve dependency for ':app@releaseUnitTest/compileClasspath': Could not find any version that matches com.android.support:appcompat-v7:29.+.
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经过实验，解决的方法如下：

1. 打开File->Project Structure

2.打开app->Properties

将Compile Sdk Version修改为API 27

点击保存

3. 打开build.gradle文件(Module:app)

将 v7:29.+ 改为v7:27.+  ，重新编译问题解决。