Android Studio : unmappable character for encoding UTF-8

I have encountered this problem, too. The reason for my problem is that I copy a file which is not encoded UTF-8 from Eclipse to Android Studio. A solution to this problem is that:

1. Make sure the default file encoding of your Android Studio is UTF-8: Settings --> File Encodings, set IDE Encoding, Project Encoding and Default encoding for properties files to UTF-8.
2. Copy your error file to a txt file and delete the error file.
3. Create a new file, its name is as the same as the deleted file.
4. Copy the content from the txt file to the new file.

Adding the following to build.gradle solves the problem :

android {
    ...
    compileOptions.encoding = 'ISO-8859-1'

For Android Studio 2.2 you have To add compile option in gradle file of your project:

android { ... compileOptions { encoding "ISO-8859-1" sourceCompatibility JavaVersion.VERSION_1_7 targetCompatibility JavaVersion.VERSION_1_7 } }