Android gradle文件中缺少库和其他包含项

当我打开'build.Gradle'时，我收到一个R文件的错误。我在文件里找到了这个，所有的图书馆都不见了

我试图清除缓存并重新启动android studio

请帮我摆脱这种情况

/*
 * Copyright 2011 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.gradle.api.artifacts;

/**
 * Unsuccessfully resolved dependency.
 */
public interface UnresolvedDependency {
    /**
     * The module selector of the dependency.
     *
     * @since 1.1-rc-1
     */
    ModuleVersionSelector getSelector();

    /**
     * the exception that is the cause of unresolved state
     */
    Throwable getProblem();
}

分级属性

或者试试这个

dependencies {
classpath 'com.android.tools.build:gradle:3.2.1'
}

---

但所有的东西都从我的gradle中移除了。

dependencies {
classpath 'com.android.tools.build:gradle:3.2.1'
}