Cannot resolve symbol 'CALL_PHONE'

Cannot resolve symbol 'CALL_PHONE'是Android Studio开发中常见的错误之一，它表示在代码中使用了CALL_PHONE这个未定义的符号。这个错误通常是由于缺少相应的权限或者库文件导致的。解决这个问题的方法有以下几种：
1. 检查AndroidManifest.xml文件中是否添加了CALL_PHONE权限，如果没有，需要在文件中添加以下代码：
<uses-permission android:name="android.permission.CALL_PHONE" />
2. 检查是否导入了相应的库文件，如果没有，需要在build.gradle文件中添加以下代码：
dependencies {
implementation 'com.android.support:support-v4:28.0.0'
}
3. 如果以上两种方法都没有解决问题，可以尝试使用方法1中提到的Invalidate caches/Restart功能，重新启动Android Studio。

相关问题

Cannot resolve symbol 'ACTION_USB_STATE'

`ACTION_USB_STATE` is a constant defined in the `android.hardware.usb.UsbManager` class. It is used to broadcast USB state changes. If you are getting the error "Cannot resolve symbol 'ACTION_USB_STATE'", it means that you haven't imported the necessary class or there might be an issue with your Android project configuration.

To resolve this issue, make sure you have the following import statement at the top of your Java file:

import android.hardware.usb.UsbManager;

Also, ensure that you have the necessary permissions declared in your AndroidManifest.xml file:

<uses-permission android:name="android.permission.USB_PERMISSION" />

If you have already done these steps and still encounter the issue, try cleaning and rebuilding your project or restarting your IDE.

Cannot resolve symbol 'WRITE_EXTERNAL_STORAGE'

This error typically occurs when you are trying to use the WRITE_EXTERNAL_STORAGE permission in your Android application but have not declared it in the AndroidManifest.xml file.

To resolve this error, add the following line of code to your AndroidManifest.xml file:

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>

This will declare the WRITE_EXTERNAL_STORAGE permission and allow your application to write to external storage.