[Laravel] Referencing column and referenced column in foreign key constraint are incompatible

->unsigned()->index()

public function up()
{
    Schema::create('meals', function (Blueprint $table) {
        $table->increments('id');
        $table->integer('user_id')->unsigned();
        $table->integer('category_id')->unsigned();
        $table->string('title');
        $table->string('body');
        $table->string('meal_av');
        $table->timestamps();
        $table->foreign('user_id')
            ->references('id')
            ->on('users')
            ->onDelete('cascade');
        $table->foreign('category_id')
            ->references('id')
            ->on('categories')
            ->onDelete('cascade');
    });
}  

```

                                                                                                                                 
 Exception trace:

  1   PDOException::("SQLSTATE[HY000]: General error: 3780 Referencing column 'room_id' and referenced column 'id' in foreign key constraint 'contacts_room_id_foreign' are incompatible.")
      /Users/shaquilenoor/Desktop/chatapi/vendor/laravel/framework/src/Illuminate/Database/Connection.php:458

  2   PDOStatement::execute() 

    

$table->integer('user_id')->unsigned()->index();

$table->integer('category_id')->unsigned()->index();

https://stackoverflow.com/questions/32669880/laravel-migration-foreign-key-constraint-is-incorrectly-formed-errno-150